simplified code across the app and consolidated duplicated helpers

lib/routing/app_routes.dart

@@ -1,5 +1,6 @@
 import 'dart:async';
 
+import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
@@ -145,19 +146,17 @@ class AppRoutes {
   /// the selected element (or null if dismissed). The timetable view renders
   /// the chosen plan inline. Gated behind the `viewForeignTimetables`
   /// capability at the call site.
-  static Future<TimetableElementRef?> openElementPicker(
+  static Future<TimetableElementRef?> openElementPicker(BuildContext context) =>
+      _pushForResult(context, const ElementPickerPage());
+
+  // pushScreen casts its internal MaterialPageRoute to `Route<T>`, which blows
+  // up for a concrete (record) T — so push untyped (T = dynamic, like every
+  // other caller) and cast the popped result ourselves.
+  static Future<T?> _pushForResult<T>(
     BuildContext context,
-  ) async {
-    // pushScreen casts its internal MaterialPageRoute to `Route<T>`, which
-    // blows up for a concrete (record) T — so push untyped (T = dynamic, like
-    // every other caller) and cast the popped result ourselves.
-    final result = await pushScreen(
-      context,
-      withNavBar: false,
-      screen: const ElementPickerPage(),
-    );
-    return result as TimetableElementRef?;
-  }
+    Widget screen,
+  ) async =>
+      (await pushScreen(context, withNavBar: false, screen: screen)) as T?;
 
   /// Opens the user/group picker for sharing a file and resolves to the chosen
   /// recipient (or null if dismissed). Which kinds are offered is gated by the
@@ -166,19 +165,10 @@ class AppRoutes {
     BuildContext context, {
     required bool allowUsers,
     required bool allowGroups,
-  }) async {
-    // Push untyped (T = dynamic) and cast the popped result ourselves —
-    // pushScreen can't carry a concrete non-Widget T (see openElementPicker).
-    final result = await pushScreen(
-      context,
-      withNavBar: false,
-      screen: ShareePickerPage(
-        allowUsers: allowUsers,
-        allowGroups: allowGroups,
-      ),
-    );
-    return result as ShareeRef?;
-  }
+  }) => _pushForResult(
+    context,
+    ShareePickerPage(allowUsers: allowUsers, allowGroups: allowGroups),
+  );
 
   static void openMarianumMessage(
     BuildContext context,
@@ -452,13 +442,7 @@ class AppRoutes {
   static GetRoomResponseObject? _findRoomByToken(
     GetRoomResponse? rooms,
     String token,
-  ) {
-    if (rooms == null) return null;
-    for (final room in rooms.data) {
-      if (room.token == token) return room;
-    }
-    return null;
-  }
+  ) => rooms?.data.firstWhereOrNull((room) => room.token == token);
 
   /// Pushes a module from the "Mehr" tab list. Modules already in the bottom
   /// bar are switched to via [goToTab] instead.