Fix cross-platform builds: process cleanup and disk space checking

- Add platform-specific implementations for Windows, BSD systems
- Create platform-specific disk space checking with proper syscalls
- Add Windows process cleanup using tasklist/taskkill
- Add BSD-specific Statfs_t field handling (F_blocks, F_bavail, F_bsize)
- Support 9/10 target platforms (Linux, Windows, macOS, FreeBSD, OpenBSD)
- Process cleanup now works on all Unix-like systems and Windows
- Phase 2 TUI improvements compatible across platforms

internal/checks/disk_check_windows.go

@@ -0,0 +1,131 @@
+//go:build windows
+// +build windows
+
+package checks
+
+import (
+	"fmt"
+	"path/filepath"
+	"syscall"
+	"unsafe"
+)
+
+var (
+	kernel32           = syscall.NewLazyDLL("kernel32.dll")
+	getDiskFreeSpaceEx = kernel32.NewProc("GetDiskFreeSpaceExW")
+)
+
+// CheckDiskSpace checks available disk space for a given path (Windows implementation)
+func CheckDiskSpace(path string) *DiskSpaceCheck {
+	// Get absolute path
+	absPath, err := filepath.Abs(path)
+	if err != nil {
+		absPath = path
+	}
+
+	// Get the drive root (e.g., "C:\")
+	vol := filepath.VolumeName(absPath)
+	if vol == "" {
+		// If no volume, try current directory
+		vol = "."
+	}
+	
+	var freeBytesAvailable, totalNumberOfBytes, totalNumberOfFreeBytes uint64
+
+	// Call Windows API
+	pathPtr, _ := syscall.UTF16PtrFromString(vol)
+	ret, _, _ := getDiskFreeSpaceEx.Call(
+		uintptr(unsafe.Pointer(pathPtr)),
+		uintptr(unsafe.Pointer(&freeBytesAvailable)),
+		uintptr(unsafe.Pointer(&totalNumberOfBytes)),
+		uintptr(unsafe.Pointer(&totalNumberOfFreeBytes)))
+
+	if ret == 0 {
+		// API call failed, return error state
+		return &DiskSpaceCheck{
+			Path:       absPath,
+			Critical:   true,
+			Sufficient: false,
+		}
+	}
+
+	// Calculate usage
+	usedBytes := totalNumberOfBytes - totalNumberOfFreeBytes
+	usedPercent := float64(usedBytes) / float64(totalNumberOfBytes) * 100
+
+	check := &DiskSpaceCheck{
+		Path:           absPath,
+		TotalBytes:     totalNumberOfBytes,
+		AvailableBytes: freeBytesAvailable,
+		UsedBytes:      usedBytes,
+		UsedPercent:    usedPercent,
+	}
+
+	// Determine status thresholds
+	check.Critical = usedPercent >= 95
+	check.Warning = usedPercent >= 80 && !check.Critical
+	check.Sufficient = !check.Critical && !check.Warning
+
+	return check
+}
+
+// CheckDiskSpaceForRestore checks if there's enough space for restore (needs 4x archive size)
+func CheckDiskSpaceForRestore(path string, archiveSize int64) *DiskSpaceCheck {
+	check := CheckDiskSpace(path)
+	requiredBytes := uint64(archiveSize) * 4 // Account for decompression
+	
+	// Override status based on required space
+	if check.AvailableBytes < requiredBytes {
+		check.Critical = true
+		check.Sufficient = false
+		check.Warning = false
+	} else if check.AvailableBytes < requiredBytes*2 {
+		check.Warning = true
+		check.Sufficient = false
+	}
+	
+	return check
+}
+
+// FormatDiskSpaceMessage creates a user-friendly disk space message
+func FormatDiskSpaceMessage(check *DiskSpaceCheck) string {
+	var status string
+	var icon string
+
+	if check.Critical {
+		status = "CRITICAL"
+		icon = "❌"
+	} else if check.Warning {
+		status = "WARNING"
+		icon = "⚠️ "
+	} else {
+		status = "OK"
+		icon = "✓"
+	}
+
+	msg := fmt.Sprintf(`📊 Disk Space Check (%s):
+   Path: %s
+   Total: %s
+   Available: %s (%.1f%% used)
+   %s Status: %s`,
+		status,
+		check.Path,
+		formatBytes(check.TotalBytes),
+		formatBytes(check.AvailableBytes),
+		check.UsedPercent,
+		icon,
+		status)
+
+	if check.Critical {
+		msg += "\n   \n   ⚠️  CRITICAL: Insufficient disk space!"
+		msg += "\n   Operation blocked. Free up space before continuing."
+	} else if check.Warning {
+		msg += "\n   \n   ⚠️  WARNING: Low disk space!"
+		msg += "\n   Backup may fail if database is larger than estimated."
+	} else {
+		msg += "\n   \n   ✓ Sufficient space available"
+	}
+
+	return msg
+}
+