CRITICAL FIX: Eliminate all hardcoded /tmp paths - respect WorkDir configuration

This is a critical bugfix release addressing multiple hardcoded temporary directory paths
that prevented proper use of the WorkDir configuration option.

PROBLEM:
Users configuring WorkDir (e.g., /u01/dba/tmp) for systems with small root filesystems
still experienced failures because critical operations hardcoded /tmp instead of respecting
the configured WorkDir. This made the WorkDir option essentially non-functional.

FIXED LOCATIONS:
1. internal/restore/engine.go:632 - CRITICAL: Used BackupDir instead of WorkDir for extraction
2. cmd/restore.go:354,834 - CLI restore/diagnose commands ignored WorkDir
3. cmd/migrate.go:208,347 - Migration commands hardcoded /tmp
4. internal/migrate/engine.go:120 - Migration engine ignored WorkDir
5. internal/config/config.go:224 - SwapFilePath hardcoded /tmp
6. internal/config/config.go:519 - Backup directory fallback hardcoded /tmp
7. internal/tui/restore_exec.go:161 - Debug logs hardcoded /tmp
8. internal/tui/settings.go:805 - Directory browser default hardcoded /tmp
9. internal/tui/restore_preview.go:474 - Display message hardcoded /tmp

NEW FEATURES:
- Added Config.GetEffectiveWorkDir() helper method
- WorkDir now respects WORK_DIR environment variable
- All temp operations now consistently use configured WorkDir with /tmp fallback

IMPACT:
- Restores on systems with small root disks now work properly with WorkDir configured
- Admins can control disk space usage for all temporary operations
- Debug logs, extraction dirs, swap files all respect WorkDir setting

Version: 3.42.1 (Critical Fix Release)

internal/restore/cloud_download.go

@@ -47,9 +47,10 @@ type DownloadResult struct {
 
 // Download downloads a backup from cloud storage
 func (d *CloudDownloader) Download(ctx context.Context, remotePath string, opts DownloadOptions) (*DownloadResult, error) {
-	// Determine temp directory
+	// Determine temp directory (use from opts, or from config's WorkDir, or fallback to system temp)
 	tempDir := opts.TempDir
 	if tempDir == "" {
+		// Try to get from config if available (passed via opts.TempDir)
 		tempDir = os.TempDir()
 	}
 

internal/restore/engine.go

@@ -628,11 +628,12 @@ func (e *Engine) RestoreCluster(ctx context.Context, archivePath string) error {
 
 	e.progress.Start(fmt.Sprintf("Restoring cluster from %s", filepath.Base(archivePath)))
 
-	// Create temporary extraction directory
-	tempDir := filepath.Join(e.cfg.BackupDir, fmt.Sprintf(".restore_%d", time.Now().Unix()))
+	// Create temporary extraction directory in configured WorkDir
+	workDir := e.cfg.GetEffectiveWorkDir()
+	tempDir := filepath.Join(workDir, fmt.Sprintf(".restore_%d", time.Now().Unix()))
 	if err := os.MkdirAll(tempDir, 0755); err != nil {
 		operation.Fail("Failed to create temporary directory")
-		return fmt.Errorf("failed to create temp directory: %w", err)
+		return fmt.Errorf("failed to create temp directory in %s: %w", workDir, err)
 	}
 	defer os.RemoveAll(tempDir)