opt.: auto add date for manual webdav backup

lib/core/extension/datetime.dart

@@ -2,4 +2,14 @@ extension DateTimeX on DateTime {
   String get hourMinute {
     return '${hour.toString().padLeft(2, '0')}:${minute.toString().padLeft(2, '0')}';
   }
+
+  /// Format: 2021-01-01-0000
+  String get numStr {
+    final year = this.year.toString();
+    final month = this.month.toString().padLeft(2, '0');
+    final day = this.day.toString().padLeft(2, '0');
+    final hour = this.hour.toString().padLeft(2, '0');
+    final minute = this.minute.toString().padLeft(2, '0');
+    return '$year-$month-$day-$hour$minute';
+  }
 }

lib/core/utils/sync/webdav.dart

@@ -73,6 +73,21 @@ abstract final class Webdav {
     return null;
   }
 
+  static Future<List<String>> list() async {
+    try {
+      final list = await _client.readDir(_prefix);
+      final names = <String>[];
+      for (final item in list) {
+        if ((item.isDir ?? true) || item.name == null) continue;
+        names.add(item.name!);
+      }
+      return names;
+    } catch (e, s) {
+      _logger.warning('List failed', e, s);
+      return [];
+    }
+  }
+
   static void changeClient(String url, String user, String pwd) {
     _client = WebdavClient(url: url, user: user, pwd: pwd);
     Stores.setting.webdavUrl.put(url);