feat: Add bulk delete and merge functionality for inventory items with DTOs and API endpoints

flutter/lib/core/api/api_paths.dart

@@ -59,6 +59,8 @@ class RecipeApiPaths {
 
 class InventoryApiPaths {
   static const list = '/inventory';
+  static const mergeMany = '/inventory/merge-many';
+  static const bulkDelete = '/inventory/bulk-delete';
   static String update(int id) => '/inventory/$id';
   static String remove(int id) => '/inventory/$id';
   static String moveToPantry(int id) => '/inventory/$id/move-to-pantry';

flutter/lib/core/ui/app_shell.dart

@@ -168,12 +168,19 @@ class AppShell extends ConsumerWidget {
           PopupMenuButton<String>(
             tooltip: 'Profil och konto',
             icon: const Icon(Icons.account_circle_outlined),
-            onSelected: (value) {
+            onSelected: (value) async {
               switch (value) {
                 case 'profile':
                   if (location != '/profile' && context.mounted) {
                     onNavigateToPath('/profile');
                   }
+                  break;
+                case 'logout':
+                  await ref.read(authStateProvider.notifier).logout();
+                  if (context.mounted) {
+                    onNavigateToPath('/login');
+                  }
+                  break;
               }
             },
             itemBuilder: (context) => const [
@@ -185,6 +192,15 @@ class AppShell extends ConsumerWidget {
                   contentPadding: EdgeInsets.zero,
                 ),
               ),
+              PopupMenuDivider(),
+              PopupMenuItem<String>(
+                value: 'logout',
+                child: ListTile(
+                  leading: Icon(Icons.logout),
+                  title: Text('Logga ut'),
+                  contentPadding: EdgeInsets.zero,
+                ),
+              ),
             ],
           ),
         ],