feat: Implement server data deletion functionality with confirmation dialog in SettingsScreen

lib/data/api_client.dart

@@ -217,6 +217,35 @@ class AuthApi {
     }
   }
 
+  Future<Map<String, dynamic>> deleteAllServerData({String? endpoint}) async {
+    final String? token = await accessToken;
+    if (token == null) {
+      return {'error': true, 'message': 'No access token available'};
+    }
+
+    final String base = endpoint ?? await ApiConfig.getEndpoint();
+    final Uri url = Uri.parse('$base/auth/delete-all-data');
+
+    final http.Response res = await http.post(
+      url,
+      headers: {
+        'Content-Type': 'application/json',
+        'Authorization': 'Bearer $token',
+      },
+    );
+
+    if (res.statusCode >= 200 && res.statusCode < 300) {
+      return {'error': false, 'status': res.statusCode, 'body': res.body};
+    }
+
+    try {
+      final dynamic decoded = jsonDecode(res.body);
+      return {'error': true, 'status': res.statusCode, 'body': decoded};
+    } catch (_) {
+      return {'error': true, 'status': res.statusCode, 'body': res.body};
+    }
+  }
+
   List<int> _randomBytes(int length) {
     final Random random = Random.secure();
     return List<int>.generate(length, (_) => random.nextInt(256));