Add WireGuard TUI implementation

- Add Go TUI with bubbletea for WireGuard management
- Implement client CRUD operations with QR code generation
- Add configuration and validation modules
- Install/update scripts for client setup
- Update Makefile to build binaries to bin/ directory
- Add .gitignore for Go projects

internal/backup/restore.go

@@ -0,0 +1,122 @@
+package backup
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+// ValidateBackup checks if a backup exists and is valid
+func ValidateBackup(backupName string) error {
+	backupDir := "/etc/wg-admin/backups"
+	backupPath := filepath.Join(backupDir, backupName)
+
+	// Check if backup directory exists
+	info, err := os.Stat(backupPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return fmt.Errorf("backup '%s' does not exist", backupName)
+		}
+		return fmt.Errorf("failed to access backup '%s': %w", backupName, err)
+	}
+
+	// Check if it's a directory
+	if !info.IsDir() {
+		return fmt.Errorf("'%s' is not a valid backup directory", backupName)
+	}
+
+	// Check for required files
+	metadataPath := filepath.Join(backupPath, "backup-info.txt")
+	if _, err := os.Stat(metadataPath); os.IsNotExist(err) {
+		return fmt.Errorf("backup '%s' is missing required metadata", backupName)
+	}
+
+	// Check for wireguard directory
+	wgBackupPath := filepath.Join(backupPath, "wireguard")
+	if _, err := os.Stat(wgBackupPath); os.IsNotExist(err) {
+		return fmt.Errorf("backup '%s' is missing wireguard configuration", backupName)
+	}
+
+	return nil
+}
+
+// ReloadWireGuard reloads the WireGuard interface to apply configuration changes
+func ReloadWireGuard() error {
+	interfaceName := "wg0"
+
+	// Try to down the interface first
+	cmdDown := exec.Command("wg-quick", "down", interfaceName)
+	_ = cmdDown.Run() // Ignore errors if interface is not up
+
+	// Bring the interface up
+	cmdUp := exec.Command("wg-quick", "up", interfaceName)
+	output, err := cmdUp.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("failed to reload wireguard interface: %w, output: %s", err, string(output))
+	}
+
+	return nil
+}
+
+// GetBackupSize calculates the total size of a backup directory
+func GetBackupSize(backupName string) (int64, error) {
+	backupDir := "/etc/wg-admin/backups"
+	backupPath := filepath.Join(backupDir, backupName)
+
+	var size int64
+
+	err := filepath.Walk(backupPath, func(_ string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if !info.IsDir() {
+			size += info.Size()
+		}
+		return nil
+	})
+
+	return size, err
+}
+
+// GetBackupPath returns the full path for a backup name
+func GetBackupPath(backupName string) string {
+	return filepath.Join("/etc/wg-admin/backups", backupName)
+}
+
+// ParseBackupName extracts operation and timestamp from backup directory name
+// Format: wg-backup-{operation}-{timestamp}
+func ParseBackupName(backupName string) (operation, timestamp string, err error) {
+	if !strings.HasPrefix(backupName, "wg-backup-") {
+		return "", "", fmt.Errorf("invalid backup name format")
+	}
+
+	nameWithoutPrefix := strings.TrimPrefix(backupName, "wg-backup-")
+
+	// Timestamp format: 20060102-150405 (15 chars)
+	if len(nameWithoutPrefix) < 16 {
+		return "", "", fmt.Errorf("backup name too short")
+	}
+
+	// Extract operation (everything before last timestamp)
+	timestampLen := 15
+	if len(nameWithoutPrefix) > timestampLen+1 {
+		operation = nameWithoutPrefix[:len(nameWithoutPrefix)-timestampLen-1]
+		// Remove trailing dash if present
+		if strings.HasSuffix(operation, "-") {
+			operation = operation[:len(operation)-1]
+		}
+	}
+
+	// Extract timestamp
+	timestamp = nameWithoutPrefix[len(nameWithoutPrefix)-timestampLen:]
+
+	// Validate timestamp format
+	if _, err := time.Parse("20060102-150405", timestamp); err != nil {
+		return "", "", fmt.Errorf("invalid timestamp format in backup name: %w", err)
+	}
+
+	return operation, timestamp, nil
+}