Add removable mock mode for a clickable preview

Runs the whole app on seeded in-memory data with no backend or device
storage, behind useMockData in lib/Grounded/mock/MockSwitch.dart. To
remove: delete lib/Grounded/mock/ and the lines tagged "MOCK:" in
ParentViewModel (or revert this commit, keeping the notification guard).

Also skips local notifications on web, where the plugin and dart:io
Platform both throw.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KhQh614DMeYoQEH9SoMRUw

frontend/lib/Grounded/see/parent/ParentViewModel.dart

@@ -18,6 +18,9 @@ import '../../designs/text/Text.dart';
 import '../../informatics/AppDataManager.dart';
 import '../../informatics/DataManager.dart';
 import '../../memory/InternalMemory.dart';
+import '../../mock/MockComms.dart'; // MOCK: remove with lib/Grounded/mock/
+import '../../mock/MockMemory.dart'; // MOCK: remove with lib/Grounded/mock/
+import '../../mock/MockSwitch.dart'; // MOCK: remove with lib/Grounded/mock/
 import '../../utils/Colors.dart';
 import '../system/sessionexpired/SessionExpired.dart';
 import '../system/updateme/UpdateMe.dart';
@@ -41,7 +44,11 @@ class ParentViewModel extends ChangeNotifier {
   ParentViewModel(this.context) {
     overlayState = Overlay.of(context);
     dataManager =
-        AppDataManager(InternalMemory(), Comms(InternalMemory()), FileStorage());
+        // MOCK: restore to the single real line below when removing mocks.
+        useMockData
+            ? AppDataManager(MockMemory(), MockComms(), FileStorage())
+            : AppDataManager(
+                InternalMemory(), Comms(InternalMemory()), FileStorage());
   }
 
   DataManager getDataManager() {
@@ -199,6 +206,11 @@ class ParentViewModel extends ChangeNotifier {
   Future<bool> hasNetwork(Function() actions) async {
     closeLoading();
 
+    // MOCK: mock mode never needs a connection.
+    if (useMockData) {
+      return true;
+    }
+
     List<ConnectivityResult> resultList =
         await (Connectivity().checkConnectivity());