Refactor CLI to use flags instead of positional arguments

- Change all commands to use flags (--bucket, --prefix, etc.)
- Add --config flag to backup command
- Support VAULTIK_CONFIG environment variable for config path
- Use /etc/vaultik/config.yml as default config location
- Add test/config.yaml for testing
- Update tests to use environment variable for config path
- Add .gitignore for build artifacts and local configs
- Update documentation to reflect new CLI syntax

internal/cli/restore.go

@@ -20,22 +20,36 @@ type RestoreOptions struct {
 
 // NewRestoreCommand creates the restore command
 func NewRestoreCommand() *cobra.Command {
+	opts := &RestoreOptions{}
+
 	cmd := &cobra.Command{
-		Use:   "restore <bucket> <prefix> <snapshot_id> <target_dir>",
+		Use:   "restore",
 		Short: "Restore files from backup",
 		Long:  `Download and decrypt files from a backup snapshot`,
-		Args:  cobra.ExactArgs(4),
+		Args:  cobra.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			opts := &RestoreOptions{
-				Bucket:     args[0],
-				Prefix:     args[1],
-				SnapshotID: args[2],
-				TargetDir:  args[3],
+			// Validate required flags
+			if opts.Bucket == "" {
+				return fmt.Errorf("--bucket is required")
+			}
+			if opts.Prefix == "" {
+				return fmt.Errorf("--prefix is required")
+			}
+			if opts.SnapshotID == "" {
+				return fmt.Errorf("--snapshot is required")
+			}
+			if opts.TargetDir == "" {
+				return fmt.Errorf("--target is required")
 			}
 			return runRestore(cmd.Context(), opts)
 		},
 	}
 
+	cmd.Flags().StringVar(&opts.Bucket, "bucket", "", "S3 bucket name")
+	cmd.Flags().StringVar(&opts.Prefix, "prefix", "", "S3 prefix")
+	cmd.Flags().StringVar(&opts.SnapshotID, "snapshot", "", "Snapshot ID to restore")
+	cmd.Flags().StringVar(&opts.TargetDir, "target", "", "Target directory for restore")
+
 	return cmd
 }