feat(web): improve web build configuration and accessibility

- Add source maps and web renderer build arguments with defaults
- Configure Caddy with CSP headers, cache policies, and service worker handling
- Defer loading of import screen for performance optimization
- Add semantic labels to icons for accessibility
- Update web index.html with Swedish language, meta tags, and description
- Add robots.txt and lighthouse configuration
- Add new planning documents and archive entries

flutter/lib/core/router/app_router.dart

@@ -21,22 +21,55 @@ import '../../features/inventory/presentation/consume_inventory_screen.dart';
 import '../../features/inventory/presentation/consumption_history_screen.dart';
 import '../../features/meal_plan/presentation/meal_plan_screen.dart';
 import '../../features/pantry/presentation/pantry_screen.dart';
-import '../../features/import/presentation/import_screen.dart';
-import '../../features/shopping_list/presentation/shopping_list_screen.dart';
-import '../../features/admin/presentation/admin_screen.dart';
+import '../../features/import/presentation/import_screen.dart'
+    deferred as import_ui;
+import '../../features/shopping_list/presentation/shopping_list_screen.dart';
+import '../../features/admin/presentation/admin_screen.dart';
 
 int? _shellBranchIndexForPath(String path) {
   if (path.startsWith('/recipes')) return 0;
   if (path.startsWith('/inventory')) return 1;
   if (path.startsWith('/matsedel')) return 2;
   if (path.startsWith('/baslager')) return 3;
-  if (path.startsWith('/import')) return 4;
-  if (path.startsWith('/inkopslista')) return 5;
-  if (path.startsWith('/profile')) return 6;
-  if (path.startsWith('/admin')) return 7;
+  if (path.startsWith('/import')) return 4;
+  if (path.startsWith('/inkopslista')) return 5;
+  if (path.startsWith('/profile')) return 6;
+  if (path.startsWith('/admin')) return 7;
   return null;
 }
 
+class _DeferredRouteLoader extends StatelessWidget {
+  const _DeferredRouteLoader({
+    required this.loadLibrary,
+    required this.builder,
+  });
+
+  final Future<void> Function() loadLibrary;
+  final WidgetBuilder builder;
+
+  @override
+  Widget build(BuildContext context) {
+    return FutureBuilder<void>(
+      future: loadLibrary(),
+      builder: (context, snapshot) {
+        if (snapshot.connectionState != ConnectionState.done) {
+          return const Scaffold(
+            body: LoadingStateView(label: 'Laddar vy...'),
+          );
+        }
+        if (snapshot.hasError) {
+          return Scaffold(
+            body: Center(
+              child: Text('Kunde inte ladda sidan: ${snapshot.error}'),
+            ),
+          );
+        }
+        return builder(context);
+      },
+    );
+  }
+}
+
 final appRouterProvider = Provider<GoRouter>((ref) {
   final authState = ref.watch(authStateProvider);
 
@@ -244,26 +277,29 @@ final appRouterProvider = Provider<GoRouter>((ref) {
               ),
             ],
           ),
-          StatefulShellBranch(
-            routes: [
-              GoRoute(
-                path: '/import',
-                builder: (context, state) => const ImportScreen(),
-              ),
-            ],
-          ),
-          StatefulShellBranch(
-            routes: [
-              GoRoute(
-                path: '/inkopslista',
-                builder: (context, state) => const ShoppingListScreen(),
-              ),
-            ],
-          ),
-          StatefulShellBranch(
-            routes: [
-              GoRoute(
-                path: '/profile',
+          StatefulShellBranch(
+            routes: [
+              GoRoute(
+                path: '/import',
+                builder: (context, state) => _DeferredRouteLoader(
+                  loadLibrary: import_ui.loadLibrary,
+                  builder: (_) => import_ui.ImportScreen(),
+                ),
+              ),
+            ],
+          ),
+          StatefulShellBranch(
+            routes: [
+              GoRoute(
+                path: '/inkopslista',
+                builder: (context, state) => const ShoppingListScreen(),
+              ),
+            ],
+          ),
+          StatefulShellBranch(
+            routes: [
+              GoRoute(
+                path: '/profile',
                 builder: (context, state) => const ProfileScreen(),
               ),
             ],
@@ -273,7 +309,8 @@ final appRouterProvider = Provider<GoRouter>((ref) {
               GoRoute(
                 path: '/admin',
                 redirect: (context, state) {
-                  final token = ref.read(authStateProvider)
+                  final token = ref
+                      .read(authStateProvider)
                       .maybeWhen(data: (t) => t, orElse: () => null);
                   return jwtIsAdmin(token) ? null : '/recipes';
                 },

flutter/lib/core/ui/app_shell.dart

@@ -181,9 +181,14 @@ class AppShell extends ConsumerWidget {
                       tooltip: view.mode == RecipesViewMode.grid
                           ? 'Visa som lista'
                           : 'Visa som grid',
-                      icon: Icon(view.mode == RecipesViewMode.grid
-                          ? Icons.view_list
-                          : Icons.grid_view),
+                      icon: Icon(
+                        view.mode == RecipesViewMode.grid
+                            ? Icons.view_list
+                            : Icons.grid_view,
+                        semanticLabel: view.mode == RecipesViewMode.grid
+                            ? 'Visa som lista'
+                            : 'Visa som grid',
+                      ),
                       onPressed: () =>
                           ref.read(recipesViewProvider.notifier).toggleMode(),
                     ),
@@ -207,7 +212,10 @@ class AppShell extends ConsumerWidget {
             ),
           PopupMenuButton<String>(
             tooltip: 'Profil och konto',
-            icon: const Icon(Icons.account_circle_outlined),
+            icon: const Icon(
+              Icons.account_circle_outlined,
+              semanticLabel: 'Profil och konto',
+            ),
             onSelected: (value) async {
               switch (value) {
                 case 'profile':