refactor: remove unreachable code paths and unused members

Drops dead code across services, models, utils and widgets, including the
connection auth service, which had no implementer, and the Live TV DVR
provisioning models, which had no caller.

Tests that only covered deleted behaviour are removed or trimmed. No
behaviour change.

lib/services/jellyfin_client/parts/metadata_edit.dart

@@ -43,13 +43,6 @@ mixin _JellyfinMetadataEditMethods on MediaServerCacheMixin {
     return data is Map<String, dynamic> ? data : const <String, dynamic>{};
   }
 
-  Future<List<Map<String, dynamic>>> getItemImageInfos(String itemId) async {
-    final response = await _http.get('/Items/${_segment(itemId)}/Images');
-    throwIfHttpError(response);
-    final data = response.data;
-    return data is List ? data.whereType<Map<String, dynamic>>().toList() : const <Map<String, dynamic>>[];
-  }
-
   Future<bool> downloadRemoteImage(String itemId, {required String imageType, required String imageUrl}) async {
     final response = await _http.post(
       '/Items/${_segment(itemId)}/RemoteImages/Download',