simplify: dedupe boilerplate and remove dead code across all layers

lib/api/marianumconnect/queries/timetable_get_students/timetable_get_students.dart

@@ -4,13 +4,11 @@ import 'timetable_get_students_response.dart';
 class TimetableGetStudents extends MarianumConnectQuery {
   TimetableGetStudents({super.dio});
 
-  Future<TimetableGetStudentsResponse> run() => guard(() async {
-    final response = await dio.get<List<dynamic>>(
-      endpoint('timetable/elements/students'),
-    );
-    final list = response.data!
-        .map((e) => McTimetableStudent.fromJson(e as Map<String, dynamic>))
-        .toList();
-    return TimetableGetStudentsResponse(result: list);
-  });
+  Future<TimetableGetStudentsResponse> run() async =>
+      TimetableGetStudentsResponse(
+        result: await getList(
+          'timetable/elements/students',
+          McTimetableStudent.fromJson,
+        ),
+      );
 }