feat: add undergraduate import and exam selection screens

mobile/test/support/fake_school_web.dart

@@ -1,9 +1,16 @@
 import 'dart:async';
+
+import 'package:flutter/widgets.dart';
+
 import 'dart:convert';
 
 import 'package:webview_flutter_platform_interface/webview_flutter_platform_interface.dart';
 
 class FakeSchoolPlatform extends WebViewPlatform {
+  @override
+  PlatformWebViewWidget createPlatformWebViewWidget(
+    PlatformWebViewWidgetCreationParams params,
+  ) => FakeSchoolWidget(params);
   int controllerCreations = 0;
   late FakeSchoolWeb web;
   late FakeSchoolDelegate delegate;
@@ -26,6 +33,13 @@ class FakeSchoolPlatform extends WebViewPlatform {
   ) => cookies;
 }
 
+class FakeSchoolWidget extends PlatformWebViewWidget {
+  FakeSchoolWidget(super.params) : super.implementation();
+  @override
+  Widget build(BuildContext context) =>
+      const SizedBox.expand(key: Key('fake-school-browser'));
+}
+
 class FakeSchoolWeb extends PlatformWebViewController {
   FakeSchoolWeb(super.params) : super.implementation();
   final loads = <String>[];