feat: v2.0 Sprint 2 - Cloud Storage Support (Part 1)

- Add AWS SDK v2 for S3 integration
- Implement cloud.Backend interface for multi-provider support
- Add full S3 backend with upload/download/list/delete
- Support MinIO and Backblaze B2 (S3-compatible)
- Implement progress tracking for uploads/downloads
- Add cloud commands: upload, download, list, delete

New commands:
- dbbackup cloud upload [files] - Upload backups to cloud
- dbbackup cloud download [remote] [local] - Download from cloud
- dbbackup cloud list [prefix] - List cloud backups
- dbbackup cloud delete [remote] - Delete from cloud

Configuration via flags or environment:
- --cloud-provider, --cloud-bucket, --cloud-region
- --cloud-endpoint (for MinIO/B2)
- --cloud-access-key, --cloud-secret-key

New packages:
- internal/cloud - Cloud storage abstraction layer

cmd/cloud.go

@@ -0,0 +1,394 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"dbbackup/internal/cloud"
+	"github.com/spf13/cobra"
+)
+
+var cloudCmd = &cobra.Command{
+	Use:   "cloud",
+	Short: "Cloud storage operations",
+	Long: `Manage backups in cloud storage (S3, MinIO, Backblaze B2).
+
+Supports:
+- AWS S3
+- MinIO (S3-compatible)
+- Backblaze B2 (S3-compatible)
+- Any S3-compatible storage
+
+Configuration via flags or environment variables:
+  --cloud-provider      DBBACKUP_CLOUD_PROVIDER
+  --cloud-bucket        DBBACKUP_CLOUD_BUCKET
+  --cloud-region        DBBACKUP_CLOUD_REGION
+  --cloud-endpoint      DBBACKUP_CLOUD_ENDPOINT
+  --cloud-access-key    DBBACKUP_CLOUD_ACCESS_KEY (or AWS_ACCESS_KEY_ID)
+  --cloud-secret-key    DBBACKUP_CLOUD_SECRET_KEY (or AWS_SECRET_ACCESS_KEY)`,
+}
+
+var cloudUploadCmd = &cobra.Command{
+	Use:   "upload [backup-file]",
+	Short: "Upload backup to cloud storage",
+	Long: `Upload one or more backup files to cloud storage.
+
+Examples:
+  # Upload single backup
+  dbbackup cloud upload /backups/mydb.dump
+
+  # Upload with progress
+  dbbackup cloud upload /backups/mydb.dump --verbose
+
+  # Upload multiple files
+  dbbackup cloud upload /backups/*.dump`,
+	Args: cobra.MinimumNArgs(1),
+	RunE: runCloudUpload,
+}
+
+var cloudDownloadCmd = &cobra.Command{
+	Use:   "download [remote-file] [local-path]",
+	Short: "Download backup from cloud storage",
+	Long: `Download a backup file from cloud storage.
+
+Examples:
+  # Download to current directory
+  dbbackup cloud download mydb.dump .
+
+  # Download to specific path
+  dbbackup cloud download mydb.dump /backups/mydb.dump
+
+  # Download with progress
+  dbbackup cloud download mydb.dump . --verbose`,
+	Args: cobra.ExactArgs(2),
+	RunE: runCloudDownload,
+}
+
+var cloudListCmd = &cobra.Command{
+	Use:   "list [prefix]",
+	Short: "List backups in cloud storage",
+	Long: `List all backup files in cloud storage.
+
+Examples:
+  # List all backups
+  dbbackup cloud list
+
+  # List backups with prefix
+  dbbackup cloud list mydb_
+
+  # List with detailed information
+  dbbackup cloud list --verbose`,
+	Args: cobra.MaximumNArgs(1),
+	RunE: runCloudList,
+}
+
+var cloudDeleteCmd = &cobra.Command{
+	Use:   "delete [remote-file]",
+	Short: "Delete backup from cloud storage",
+	Long: `Delete a backup file from cloud storage.
+
+Examples:
+  # Delete single backup
+  dbbackup cloud delete mydb_20251125.dump
+
+  # Delete with confirmation
+  dbbackup cloud delete mydb.dump --confirm`,
+	Args: cobra.ExactArgs(1),
+	RunE: runCloudDelete,
+}
+
+var (
+	cloudProvider  string
+	cloudBucket    string
+	cloudRegion    string
+	cloudEndpoint  string
+	cloudAccessKey string
+	cloudSecretKey string
+	cloudPrefix    string
+	cloudVerbose   bool
+	cloudConfirm   bool
+)
+
+func init() {
+	rootCmd.AddCommand(cloudCmd)
+	cloudCmd.AddCommand(cloudUploadCmd, cloudDownloadCmd, cloudListCmd, cloudDeleteCmd)
+
+	// Cloud configuration flags
+	for _, cmd := range []*cobra.Command{cloudUploadCmd, cloudDownloadCmd, cloudListCmd, cloudDeleteCmd} {
+		cmd.Flags().StringVar(&cloudProvider, "cloud-provider", getEnv("DBBACKUP_CLOUD_PROVIDER", "s3"), "Cloud provider (s3, minio, b2)")
+		cmd.Flags().StringVar(&cloudBucket, "cloud-bucket", getEnv("DBBACKUP_CLOUD_BUCKET", ""), "Bucket name")
+		cmd.Flags().StringVar(&cloudRegion, "cloud-region", getEnv("DBBACKUP_CLOUD_REGION", "us-east-1"), "Region")
+		cmd.Flags().StringVar(&cloudEndpoint, "cloud-endpoint", getEnv("DBBACKUP_CLOUD_ENDPOINT", ""), "Custom endpoint (for MinIO)")
+		cmd.Flags().StringVar(&cloudAccessKey, "cloud-access-key", getEnv("DBBACKUP_CLOUD_ACCESS_KEY", getEnv("AWS_ACCESS_KEY_ID", "")), "Access key")
+		cmd.Flags().StringVar(&cloudSecretKey, "cloud-secret-key", getEnv("DBBACKUP_CLOUD_SECRET_KEY", getEnv("AWS_SECRET_ACCESS_KEY", "")), "Secret key")
+		cmd.Flags().StringVar(&cloudPrefix, "cloud-prefix", getEnv("DBBACKUP_CLOUD_PREFIX", ""), "Key prefix")
+		cmd.Flags().BoolVarP(&cloudVerbose, "verbose", "v", false, "Verbose output")
+	}
+
+	cloudDeleteCmd.Flags().BoolVar(&cloudConfirm, "confirm", false, "Skip confirmation prompt")
+}
+
+func getEnv(key, defaultValue string) string {
+	if value := os.Getenv(key); value != "" {
+		return value
+	}
+	return defaultValue
+}
+
+func getCloudBackend() (cloud.Backend, error) {
+	cfg := &cloud.Config{
+		Provider:   cloudProvider,
+		Bucket:     cloudBucket,
+		Region:     cloudRegion,
+		Endpoint:   cloudEndpoint,
+		AccessKey:  cloudAccessKey,
+		SecretKey:  cloudSecretKey,
+		Prefix:     cloudPrefix,
+		UseSSL:     true,
+		PathStyle:  cloudProvider == "minio",
+		Timeout:    300,
+		MaxRetries: 3,
+	}
+
+	if cfg.Bucket == "" {
+		return nil, fmt.Errorf("bucket name is required (use --cloud-bucket or DBBACKUP_CLOUD_BUCKET)")
+	}
+
+	backend, err := cloud.NewBackend(cfg)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create cloud backend: %w", err)
+	}
+
+	return backend, nil
+}
+
+func runCloudUpload(cmd *cobra.Command, args []string) error {
+	backend, err := getCloudBackend()
+	if err != nil {
+		return err
+	}
+
+	ctx := context.Background()
+
+	// Expand glob patterns
+	var files []string
+	for _, pattern := range args {
+		matches, err := filepath.Glob(pattern)
+		if err != nil {
+			return fmt.Errorf("invalid pattern %s: %w", pattern, err)
+		}
+		if len(matches) == 0 {
+			files = append(files, pattern)
+		} else {
+			files = append(files, matches...)
+		}
+	}
+
+	fmt.Printf("☁️  Uploading %d file(s) to %s...\n\n", len(files), backend.Name())
+
+	successCount := 0
+	for _, localPath := range files {
+		filename := filepath.Base(localPath)
+		fmt.Printf("📤 %s\n", filename)
+
+		// Progress callback
+		var lastPercent int
+		progress := func(transferred, total int64) {
+			if !cloudVerbose {
+				return
+			}
+			percent := int(float64(transferred) / float64(total) * 100)
+			if percent != lastPercent && percent%10 == 0 {
+				fmt.Printf("   Progress: %d%% (%s / %s)\n", 
+					percent, 
+					cloud.FormatSize(transferred), 
+					cloud.FormatSize(total))
+				lastPercent = percent
+			}
+		}
+
+		err := backend.Upload(ctx, localPath, filename, progress)
+		if err != nil {
+			fmt.Printf("   ❌ Failed: %v\n\n", err)
+			continue
+		}
+
+		// Get file size
+		if info, err := os.Stat(localPath); err == nil {
+			fmt.Printf("   ✅ Uploaded (%s)\n\n", cloud.FormatSize(info.Size()))
+		} else {
+			fmt.Printf("   ✅ Uploaded\n\n")
+		}
+		successCount++
+	}
+
+	fmt.Println(strings.Repeat("─", 50))
+	fmt.Printf("✅ Successfully uploaded %d/%d file(s)\n", successCount, len(files))
+
+	return nil
+}
+
+func runCloudDownload(cmd *cobra.Command, args []string) error {
+	backend, err := getCloudBackend()
+	if err != nil {
+		return err
+	}
+
+	ctx := context.Background()
+	remotePath := args[0]
+	localPath := args[1]
+
+	// If localPath is a directory, use the remote filename
+	if info, err := os.Stat(localPath); err == nil && info.IsDir() {
+		localPath = filepath.Join(localPath, filepath.Base(remotePath))
+	}
+
+	fmt.Printf("☁️  Downloading from %s...\n\n", backend.Name())
+	fmt.Printf("📥 %s → %s\n", remotePath, localPath)
+
+	// Progress callback
+	var lastPercent int
+	progress := func(transferred, total int64) {
+		if !cloudVerbose {
+			return
+		}
+		percent := int(float64(transferred) / float64(total) * 100)
+		if percent != lastPercent && percent%10 == 0 {
+			fmt.Printf("   Progress: %d%% (%s / %s)\n", 
+				percent, 
+				cloud.FormatSize(transferred), 
+				cloud.FormatSize(total))
+			lastPercent = percent
+		}
+	}
+
+	err = backend.Download(ctx, remotePath, localPath, progress)
+	if err != nil {
+		return fmt.Errorf("download failed: %w", err)
+	}
+
+	// Get file size
+	if info, err := os.Stat(localPath); err == nil {
+		fmt.Printf("   ✅ Downloaded (%s)\n", cloud.FormatSize(info.Size()))
+	} else {
+		fmt.Printf("   ✅ Downloaded\n")
+	}
+
+	return nil
+}
+
+func runCloudList(cmd *cobra.Command, args []string) error {
+	backend, err := getCloudBackend()
+	if err != nil {
+		return err
+	}
+
+	ctx := context.Background()
+	prefix := ""
+	if len(args) > 0 {
+		prefix = args[0]
+	}
+
+	fmt.Printf("☁️  Listing backups in %s/%s...\n\n", backend.Name(), cloudBucket)
+
+	backups, err := backend.List(ctx, prefix)
+	if err != nil {
+		return fmt.Errorf("failed to list backups: %w", err)
+	}
+
+	if len(backups) == 0 {
+		fmt.Println("No backups found")
+		return nil
+	}
+
+	var totalSize int64
+	for _, backup := range backups {
+		totalSize += backup.Size
+		
+		if cloudVerbose {
+			fmt.Printf("📦 %s\n", backup.Name)
+			fmt.Printf("   Size: %s\n", cloud.FormatSize(backup.Size))
+			fmt.Printf("   Modified: %s\n", backup.LastModified.Format(time.RFC3339))
+			if backup.StorageClass != "" {
+				fmt.Printf("   Storage: %s\n", backup.StorageClass)
+			}
+			fmt.Println()
+		} else {
+			age := time.Since(backup.LastModified)
+			ageStr := formatAge(age)
+			fmt.Printf("%-50s %12s  %s\n", 
+				backup.Name, 
+				cloud.FormatSize(backup.Size),
+				ageStr)
+		}
+	}
+
+	fmt.Println(strings.Repeat("─", 50))
+	fmt.Printf("Total: %d backup(s), %s\n", len(backups), cloud.FormatSize(totalSize))
+
+	return nil
+}
+
+func runCloudDelete(cmd *cobra.Command, args []string) error {
+	backend, err := getCloudBackend()
+	if err != nil {
+		return err
+	}
+
+	ctx := context.Background()
+	remotePath := args[0]
+
+	// Check if file exists
+	exists, err := backend.Exists(ctx, remotePath)
+	if err != nil {
+		return fmt.Errorf("failed to check file: %w", err)
+	}
+	if !exists {
+		return fmt.Errorf("file not found: %s", remotePath)
+	}
+
+	// Get file info
+	size, err := backend.GetSize(ctx, remotePath)
+	if err != nil {
+		return fmt.Errorf("failed to get file info: %w", err)
+	}
+
+	// Confirmation prompt
+	if !cloudConfirm {
+		fmt.Printf("⚠️  Delete %s (%s) from cloud storage?\n", remotePath, cloud.FormatSize(size))
+		fmt.Print("Type 'yes' to confirm: ")
+		var response string
+		fmt.Scanln(&response)
+		if response != "yes" {
+			fmt.Println("Cancelled")
+			return nil
+		}
+	}
+
+	fmt.Printf("🗑️  Deleting %s...\n", remotePath)
+
+	err = backend.Delete(ctx, remotePath)
+	if err != nil {
+		return fmt.Errorf("delete failed: %w", err)
+	}
+
+	fmt.Printf("✅ Deleted %s (%s)\n", remotePath, cloud.FormatSize(size))
+
+	return nil
+}
+
+func formatAge(d time.Duration) string {
+	if d < time.Minute {
+		return "just now"
+	} else if d < time.Hour {
+		return fmt.Sprintf("%d min ago", int(d.Minutes()))
+	} else if d < 24*time.Hour {
+		return fmt.Sprintf("%d hours ago", int(d.Hours()))
+	} else {
+		return fmt.Sprintf("%d days ago", int(d.Hours()/24))
+	}
+}

go.mod

@@ -18,6 +18,25 @@ require (
 
 require (
 	filippo.io/edwards25519 v1.1.0 // indirect
+	github.com/aws/aws-sdk-go-v2 v1.40.0 // indirect
+	github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.7.3 // indirect
+	github.com/aws/aws-sdk-go-v2/config v1.32.1 // indirect
+	github.com/aws/aws-sdk-go-v2/credentials v1.19.1 // indirect
+	github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.18.14 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/configsources v1.4.14 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.7.14 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/ini v1.8.4 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/v4a v1.4.14 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.13.3 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/checksum v1.9.5 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.13.14 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/s3shared v1.19.14 // indirect
+	github.com/aws/aws-sdk-go-v2/service/s3 v1.92.0 // indirect
+	github.com/aws/aws-sdk-go-v2/service/signin v1.0.1 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sso v1.30.4 // indirect
+	github.com/aws/aws-sdk-go-v2/service/ssooidc v1.35.9 // indirect
+	github.com/aws/aws-sdk-go-v2/service/sts v1.41.1 // indirect
+	github.com/aws/smithy-go v1.23.2 // indirect
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
 	github.com/charmbracelet/x/ansi v0.10.1 // indirect

go.sum

@@ -2,6 +2,44 @@ filippo.io/edwards25519 v1.1.0 h1:FNf4tywRC1HmFuKW5xopWpigGjJKiJSV0Cqo0cJWDaA=
 filippo.io/edwards25519 v1.1.0/go.mod h1:BxyFTGdWcka3PhytdK4V28tE5sGfRvvvRV7EaN4VDT4=
 github.com/Netflix/go-expect v0.0.0-20220104043353-73e0943537d2 h1:+vx7roKuyA63nhn5WAunQHLTznkw5W8b1Xc0dNjp83s=
 github.com/Netflix/go-expect v0.0.0-20220104043353-73e0943537d2/go.mod h1:HBCaDeC1lPdgDeDbhX8XFpy1jqjK0IBG8W5K+xYqA0w=
+github.com/aws/aws-sdk-go-v2 v1.40.0 h1:/WMUA0kjhZExjOQN2z3oLALDREea1A7TobfuiBrKlwc=
+github.com/aws/aws-sdk-go-v2 v1.40.0/go.mod h1:c9pm7VwuW0UPxAEYGyTmyurVcNrbF6Rt/wixFqDhcjE=
+github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.7.3 h1:DHctwEM8P8iTXFxC/QK0MRjwEpWQeM9yzidCRjldUz0=
+github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.7.3/go.mod h1:xdCzcZEtnSTKVDOmUZs4l/j3pSV6rpo1WXl5ugNsL8Y=
+github.com/aws/aws-sdk-go-v2/config v1.32.1 h1:iODUDLgk3q8/flEC7ymhmxjfoAnBDwEEYEVyKZ9mzjU=
+github.com/aws/aws-sdk-go-v2/config v1.32.1/go.mod h1:xoAgo17AGrPpJBSLg81W+ikM0cpOZG8ad04T2r+d5P0=
+github.com/aws/aws-sdk-go-v2/credentials v1.19.1 h1:JeW+EwmtTE0yXFK8SmklrFh/cGTTXsQJumgMZNlbxfM=
+github.com/aws/aws-sdk-go-v2/credentials v1.19.1/go.mod h1:BOoXiStwTF+fT2XufhO0Efssbi1CNIO/ZXpZu87N0pw=
+github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.18.14 h1:WZVR5DbDgxzA0BJeudId89Kmgy6DIU4ORpxwsVHz0qA=
+github.com/aws/aws-sdk-go-v2/feature/ec2/imds v1.18.14/go.mod h1:Dadl9QO0kHgbrH1GRqGiZdYtW5w+IXXaBNCHTIaheM4=
+github.com/aws/aws-sdk-go-v2/internal/configsources v1.4.14 h1:PZHqQACxYb8mYgms4RZbhZG0a7dPW06xOjmaH0EJC/I=
+github.com/aws/aws-sdk-go-v2/internal/configsources v1.4.14/go.mod h1:VymhrMJUWs69D8u0/lZ7jSB6WgaG/NqHi3gX0aYf6U0=
+github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.7.14 h1:bOS19y6zlJwagBfHxs0ESzr1XCOU2KXJCWcq3E2vfjY=
+github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.7.14/go.mod h1:1ipeGBMAxZ0xcTm6y6paC2C/J6f6OO7LBODV9afuAyM=
+github.com/aws/aws-sdk-go-v2/internal/ini v1.8.4 h1:WKuaxf++XKWlHWu9ECbMlha8WOEGm0OUEZqm4K/Gcfk=
+github.com/aws/aws-sdk-go-v2/internal/ini v1.8.4/go.mod h1:ZWy7j6v1vWGmPReu0iSGvRiise4YI5SkR3OHKTZ6Wuc=
+github.com/aws/aws-sdk-go-v2/internal/v4a v1.4.14 h1:ITi7qiDSv/mSGDSWNpZ4k4Ve0DQR6Ug2SJQ8zEHoDXg=
+github.com/aws/aws-sdk-go-v2/internal/v4a v1.4.14/go.mod h1:k1xtME53H1b6YpZt74YmwlONMWf4ecM+lut1WQLAF/U=
+github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.13.3 h1:x2Ibm/Af8Fi+BH+Hsn9TXGdT+hKbDd5XOTZxTMxDk7o=
+github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.13.3/go.mod h1:IW1jwyrQgMdhisceG8fQLmQIydcT/jWY21rFhzgaKwo=
+github.com/aws/aws-sdk-go-v2/service/internal/checksum v1.9.5 h1:Hjkh7kE6D81PgrHlE/m9gx+4TyyeLHuY8xJs7yXN5C4=
+github.com/aws/aws-sdk-go-v2/service/internal/checksum v1.9.5/go.mod h1:nPRXgyCfAurhyaTMoBMwRBYBhaHI4lNPAnJmjM0Tslc=
+github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.13.14 h1:FIouAnCE46kyYqyhs0XEBDFFSREtdnr8HQuLPQPLCrY=
+github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.13.14/go.mod h1:UTwDc5COa5+guonQU8qBikJo1ZJ4ln2r1MkF7Dqag1E=
+github.com/aws/aws-sdk-go-v2/service/internal/s3shared v1.19.14 h1:FzQE21lNtUor0Fb7QNgnEyiRCBlolLTX/Z1j65S7teM=
+github.com/aws/aws-sdk-go-v2/service/internal/s3shared v1.19.14/go.mod h1:s1ydyWG9pm3ZwmmYN21HKyG9WzAZhYVW85wMHs5FV6w=
+github.com/aws/aws-sdk-go-v2/service/s3 v1.92.0 h1:8FshVvnV2sr9kOSAbOnc/vwVmmAwMjOedKH6JW2ddPM=
+github.com/aws/aws-sdk-go-v2/service/s3 v1.92.0/go.mod h1:wYNqY3L02Z3IgRYxOBPH9I1zD9Cjh9hI5QOy/eOjQvw=
+github.com/aws/aws-sdk-go-v2/service/signin v1.0.1 h1:BDgIUYGEo5TkayOWv/oBLPphWwNm/A91AebUjAu5L5g=
+github.com/aws/aws-sdk-go-v2/service/signin v1.0.1/go.mod h1:iS6EPmNeqCsGo+xQmXv0jIMjyYtQfnwg36zl2FwEouk=
+github.com/aws/aws-sdk-go-v2/service/sso v1.30.4 h1:U//SlnkE1wOQiIImxzdY5PXat4Wq+8rlfVEw4Y7J8as=
+github.com/aws/aws-sdk-go-v2/service/sso v1.30.4/go.mod h1:av+ArJpoYf3pgyrj6tcehSFW+y9/QvAY8kMooR9bZCw=
+github.com/aws/aws-sdk-go-v2/service/ssooidc v1.35.9 h1:LU8S9W/mPDAU9q0FjCLi0TrCheLMGwzbRpvUMwYspcA=
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internal/cloud/interface.go

@@ -0,0 +1,167 @@
+package cloud
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"time"
+)
+
+// Backend defines the interface for cloud storage providers
+type Backend interface {
+	// Upload uploads a file to cloud storage
+	Upload(ctx context.Context, localPath, remotePath string, progress ProgressCallback) error
+	
+	// Download downloads a file from cloud storage
+	Download(ctx context.Context, remotePath, localPath string, progress ProgressCallback) error
+	
+	// List lists all backup files in cloud storage
+	List(ctx context.Context, prefix string) ([]BackupInfo, error)
+	
+	// Delete deletes a file from cloud storage
+	Delete(ctx context.Context, remotePath string) error
+	
+	// Exists checks if a file exists in cloud storage
+	Exists(ctx context.Context, remotePath string) (bool, error)
+	
+	// GetSize returns the size of a remote file
+	GetSize(ctx context.Context, remotePath string) (int64, error)
+	
+	// Name returns the backend name (e.g., "s3", "azure", "gcs")
+	Name() string
+}
+
+// BackupInfo contains information about a backup in cloud storage
+type BackupInfo struct {
+	Key          string    // Full path/key in cloud storage
+	Name         string    // Base filename
+	Size         int64     // Size in bytes
+	LastModified time.Time // Last modification time
+	ETag         string    // Entity tag (version identifier)
+	StorageClass string    // Storage class (e.g., STANDARD, GLACIER)
+}
+
+// ProgressCallback is called during upload/download to report progress
+type ProgressCallback func(bytesTransferred, totalBytes int64)
+
+// Config contains common configuration for cloud backends
+type Config struct {
+	Provider    string // "s3", "minio", "azure", "gcs", "b2"
+	Bucket      string // Bucket or container name
+	Region      string // Region (for S3)
+	Endpoint    string // Custom endpoint (for MinIO, S3-compatible)
+	AccessKey   string // Access key or account ID
+	SecretKey   string // Secret key or access token
+	UseSSL      bool   // Use SSL/TLS (default: true)
+	PathStyle   bool   // Use path-style addressing (for MinIO)
+	Prefix      string // Prefix for all operations (e.g., "backups/")
+	Timeout     int    // Timeout in seconds (default: 300)
+	MaxRetries  int    // Maximum retry attempts (default: 3)
+	Concurrency int    // Upload/download concurrency (default: 5)
+}
+
+// NewBackend creates a new cloud storage backend based on the provider
+func NewBackend(cfg *Config) (Backend, error) {
+	switch cfg.Provider {
+	case "s3", "aws":
+		return NewS3Backend(cfg)
+	case "minio":
+		// MinIO uses S3 backend with custom endpoint
+		cfg.PathStyle = true
+		if cfg.Endpoint == "" {
+			return nil, fmt.Errorf("endpoint required for MinIO")
+		}
+		return NewS3Backend(cfg)
+	case "b2", "backblaze":
+		// Backblaze B2 uses S3-compatible API
+		cfg.PathStyle = false
+		if cfg.Endpoint == "" {
+			return nil, fmt.Errorf("endpoint required for Backblaze B2")
+		}
+		return NewS3Backend(cfg)
+	default:
+		return nil, fmt.Errorf("unsupported cloud provider: %s (supported: s3, minio, b2)", cfg.Provider)
+	}
+}
+
+// FormatSize returns human-readable size
+func FormatSize(bytes int64) string {
+	const unit = 1024
+	if bytes < unit {
+		return fmt.Sprintf("%d B", bytes)
+	}
+	div, exp := int64(unit), 0
+	for n := bytes / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %ciB", float64(bytes)/float64(div), "KMGTPE"[exp])
+}
+
+// DefaultConfig returns a config with sensible defaults
+func DefaultConfig() *Config {
+	return &Config{
+		Provider:    "s3",
+		UseSSL:      true,
+		PathStyle:   false,
+		Timeout:     300,
+		MaxRetries:  3,
+		Concurrency: 5,
+	}
+}
+
+// Validate checks if the configuration is valid
+func (c *Config) Validate() error {
+	if c.Provider == "" {
+		return fmt.Errorf("provider is required")
+	}
+	if c.Bucket == "" {
+		return fmt.Errorf("bucket name is required")
+	}
+	if c.Provider == "s3" || c.Provider == "aws" {
+		if c.Region == "" && c.Endpoint == "" {
+			return fmt.Errorf("region or endpoint is required for S3")
+		}
+	}
+	if c.Provider == "minio" || c.Provider == "b2" {
+		if c.Endpoint == "" {
+			return fmt.Errorf("endpoint is required for %s", c.Provider)
+		}
+	}
+	return nil
+}
+
+// ProgressReader wraps an io.Reader to track progress
+type ProgressReader struct {
+	reader    io.Reader
+	total     int64
+	read      int64
+	callback  ProgressCallback
+	lastReport time.Time
+}
+
+// NewProgressReader creates a progress tracking reader
+func NewProgressReader(r io.Reader, total int64, callback ProgressCallback) *ProgressReader {
+	return &ProgressReader{
+		reader:     r,
+		total:      total,
+		callback:   callback,
+		lastReport: time.Now(),
+	}
+}
+
+func (pr *ProgressReader) Read(p []byte) (int, error) {
+	n, err := pr.reader.Read(p)
+	pr.read += int64(n)
+	
+	// Report progress every 100ms or when complete
+	now := time.Now()
+	if now.Sub(pr.lastReport) > 100*time.Millisecond || err == io.EOF {
+		if pr.callback != nil {
+			pr.callback(pr.read, pr.total)
+		}
+		pr.lastReport = now
+	}
+	
+	return n, err
+}

internal/cloud/s3.go

@@ -0,0 +1,324 @@
+package cloud
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/config"
+	"github.com/aws/aws-sdk-go-v2/credentials"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+)
+
+// S3Backend implements the Backend interface for AWS S3 and compatible services
+type S3Backend struct {
+	client *s3.Client
+	bucket string
+	prefix string
+	config *Config
+}
+
+// NewS3Backend creates a new S3 backend
+func NewS3Backend(cfg *Config) (*S3Backend, error) {
+	if err := cfg.Validate(); err != nil {
+		return nil, fmt.Errorf("invalid config: %w", err)
+	}
+
+	ctx := context.Background()
+	
+	// Build AWS config
+	var awsCfg aws.Config
+	var err error
+	
+	if cfg.AccessKey != "" && cfg.SecretKey != "" {
+		// Use explicit credentials
+		credsProvider := credentials.NewStaticCredentialsProvider(
+			cfg.AccessKey,
+			cfg.SecretKey,
+			"",
+		)
+		
+		awsCfg, err = config.LoadDefaultConfig(ctx,
+			config.WithCredentialsProvider(credsProvider),
+			config.WithRegion(cfg.Region),
+		)
+	} else {
+		// Use default credential chain (environment, IAM role, etc.)
+		awsCfg, err = config.LoadDefaultConfig(ctx,
+			config.WithRegion(cfg.Region),
+		)
+	}
+	
+	if err != nil {
+		return nil, fmt.Errorf("failed to load AWS config: %w", err)
+	}
+
+	// Create S3 client with custom options
+	clientOptions := []func(*s3.Options){
+		func(o *s3.Options) {
+			if cfg.Endpoint != "" {
+				o.BaseEndpoint = aws.String(cfg.Endpoint)
+			}
+			if cfg.PathStyle {
+				o.UsePathStyle = true
+			}
+		},
+	}
+	
+	client := s3.NewFromConfig(awsCfg, clientOptions...)
+
+	return &S3Backend{
+		client: client,
+		bucket: cfg.Bucket,
+		prefix: cfg.Prefix,
+		config: cfg,
+	}, nil
+}
+
+// Name returns the backend name
+func (s *S3Backend) Name() string {
+	return "s3"
+}
+
+// buildKey creates the full S3 key from filename
+func (s *S3Backend) buildKey(filename string) string {
+	if s.prefix == "" {
+		return filename
+	}
+	return filepath.Join(s.prefix, filename)
+}
+
+// Upload uploads a file to S3
+func (s *S3Backend) Upload(ctx context.Context, localPath, remotePath string, progress ProgressCallback) error {
+	// Open local file
+	file, err := os.Open(localPath)
+	if err != nil {
+		return fmt.Errorf("failed to open file: %w", err)
+	}
+	defer file.Close()
+
+	// Get file size
+	stat, err := file.Stat()
+	if err != nil {
+		return fmt.Errorf("failed to stat file: %w", err)
+	}
+	fileSize := stat.Size()
+
+	// Create progress reader
+	var reader io.Reader = file
+	if progress != nil {
+		reader = NewProgressReader(file, fileSize, progress)
+	}
+
+	// Build S3 key
+	key := s.buildKey(remotePath)
+
+	// Upload to S3
+	_, err = s.client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+		Body:   reader,
+	})
+	
+	if err != nil {
+		return fmt.Errorf("failed to upload to S3: %w", err)
+	}
+
+	return nil
+}
+
+// Download downloads a file from S3
+func (s *S3Backend) Download(ctx context.Context, remotePath, localPath string, progress ProgressCallback) error {
+	// Build S3 key
+	key := s.buildKey(remotePath)
+
+	// Get object size first
+	size, err := s.GetSize(ctx, remotePath)
+	if err != nil {
+		return fmt.Errorf("failed to get object size: %w", err)
+	}
+
+	// Download from S3
+	result, err := s.client.GetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	})
+	if err != nil {
+		return fmt.Errorf("failed to download from S3: %w", err)
+	}
+	defer result.Body.Close()
+
+	// Create local file
+	if err := os.MkdirAll(filepath.Dir(localPath), 0755); err != nil {
+		return fmt.Errorf("failed to create directory: %w", err)
+	}
+
+	outFile, err := os.Create(localPath)
+	if err != nil {
+		return fmt.Errorf("failed to create local file: %w", err)
+	}
+	defer outFile.Close()
+
+	// Copy with progress tracking
+	var reader io.Reader = result.Body
+	if progress != nil {
+		reader = NewProgressReader(result.Body, size, progress)
+	}
+
+	_, err = io.Copy(outFile, reader)
+	if err != nil {
+		return fmt.Errorf("failed to write file: %w", err)
+	}
+
+	return nil
+}
+
+// List lists all backup files in S3
+func (s *S3Backend) List(ctx context.Context, prefix string) ([]BackupInfo, error) {
+	// Build full prefix
+	fullPrefix := s.buildKey(prefix)
+
+	// List objects
+	result, err := s.client.ListObjectsV2(ctx, &s3.ListObjectsV2Input{
+		Bucket: aws.String(s.bucket),
+		Prefix: aws.String(fullPrefix),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to list objects: %w", err)
+	}
+
+	// Convert to BackupInfo
+	var backups []BackupInfo
+	for _, obj := range result.Contents {
+		if obj.Key == nil {
+			continue
+		}
+		
+		key := *obj.Key
+		name := filepath.Base(key)
+		
+		// Skip if it's just a directory marker
+		if strings.HasSuffix(key, "/") {
+			continue
+		}
+
+		info := BackupInfo{
+			Key:          key,
+			Name:         name,
+			Size:         *obj.Size,
+			LastModified: *obj.LastModified,
+		}
+		
+		if obj.ETag != nil {
+			info.ETag = *obj.ETag
+		}
+		
+		if obj.StorageClass != "" {
+			info.StorageClass = string(obj.StorageClass)
+		} else {
+			info.StorageClass = "STANDARD"
+		}
+
+		backups = append(backups, info)
+	}
+
+	return backups, nil
+}
+
+// Delete deletes a file from S3
+func (s *S3Backend) Delete(ctx context.Context, remotePath string) error {
+	key := s.buildKey(remotePath)
+
+	_, err := s.client.DeleteObject(ctx, &s3.DeleteObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	})
+	
+	if err != nil {
+		return fmt.Errorf("failed to delete object: %w", err)
+	}
+
+	return nil
+}
+
+// Exists checks if a file exists in S3
+func (s *S3Backend) Exists(ctx context.Context, remotePath string) (bool, error) {
+	key := s.buildKey(remotePath)
+
+	_, err := s.client.HeadObject(ctx, &s3.HeadObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	})
+	
+	if err != nil {
+		// Check if it's a "not found" error
+		if strings.Contains(err.Error(), "NotFound") || strings.Contains(err.Error(), "404") {
+			return false, nil
+		}
+		return false, fmt.Errorf("failed to check object existence: %w", err)
+	}
+
+	return true, nil
+}
+
+// GetSize returns the size of a remote file
+func (s *S3Backend) GetSize(ctx context.Context, remotePath string) (int64, error) {
+	key := s.buildKey(remotePath)
+
+	result, err := s.client.HeadObject(ctx, &s3.HeadObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	})
+	
+	if err != nil {
+		return 0, fmt.Errorf("failed to get object metadata: %w", err)
+	}
+
+	if result.ContentLength == nil {
+		return 0, fmt.Errorf("content length not available")
+	}
+
+	return *result.ContentLength, nil
+}
+
+// BucketExists checks if the bucket exists and is accessible
+func (s *S3Backend) BucketExists(ctx context.Context) (bool, error) {
+	_, err := s.client.HeadBucket(ctx, &s3.HeadBucketInput{
+		Bucket: aws.String(s.bucket),
+	})
+	
+	if err != nil {
+		if strings.Contains(err.Error(), "NotFound") || strings.Contains(err.Error(), "404") {
+			return false, nil
+		}
+		return false, fmt.Errorf("failed to check bucket: %w", err)
+	}
+
+	return true, nil
+}
+
+// CreateBucket creates the bucket if it doesn't exist
+func (s *S3Backend) CreateBucket(ctx context.Context) error {
+	exists, err := s.BucketExists(ctx)
+	if err != nil {
+		return err
+	}
+	
+	if exists {
+		return nil
+	}
+
+	_, err = s.client.CreateBucket(ctx, &s3.CreateBucketInput{
+		Bucket: aws.String(s.bucket),
+	})
+	
+	if err != nil {
+		return fmt.Errorf("failed to create bucket: %w", err)
+	}
+
+	return nil
+}