refactored data providers with centralized cache resolution, unified UI using custom dialogs and bottom sheets, and enhanced network error handling for Dio and TLS errors

lib/api/marianumcloud/nextcloud_ocs.dart

@@ -1,27 +1,17 @@
 import '../../model/account_data.dart';
 import '../../model/endpoint_data.dart';
 
-/// Shared helpers for Nextcloud OCS v2 endpoints.
-///
-/// Three call sites previously duplicated the same header dictionary and the
-/// same URI scaffolding (TalkApi, AutocompleteApi, FileSharingApi). Anything
-/// that talks to `https://<domain>/<base>/ocs/v2.php/...` should go through
-/// these two helpers so additions like a new header or a different auth
-/// scheme only need to change here.
+/// Shared headers and URI builder for Nextcloud OCS v2 endpoints. Used by
+/// TalkApi, AutocompleteApi, FileSharingApi.
 class NextcloudOcs {
   NextcloudOcs._();
 
-  /// The standard OCS request header set: JSON accept, OCS API marker,
-  /// HTTP Basic auth from the active [AccountData].
   static Map<String, String> headers() => {
         'Accept': 'application/json',
         'OCS-APIRequest': 'true',
         'Authorization': AccountData().getBasicAuthHeader(),
       };
 
-  /// Builds an OCS URI by appending [pathSuffix] under `/ocs/v2.php/` of
-  /// the configured Nextcloud endpoint. Query parameters are converted to
-  /// strings (Uri rejects non-string values).
   static Uri uri(String pathSuffix, {Map<String, dynamic>? queryParameters}) {
     final endpoint = EndpointData().nextcloud();
     return Uri.https(