feat: Enhance admin panel navigation and UI by implementing tab management and improving layout structure

flutter/lib/core/ui/app_shell.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../features/auth/data/auth_providers.dart';
+import '../../features/admin/presentation/admin_screen.dart';
 import '../../features/recipes/data/recipes_grid_provider.dart';
 
 const _profileHeaderDestination = _AppDestination(
@@ -93,6 +94,7 @@ class AppShell extends ConsumerWidget {
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
+    final locationUri = Uri.parse(location);
     final isAdmin = ref.watch(isAdminProvider);
     final dests = _destinations(isAdmin);
     final selectedIndex = _selectedIndex(dests);
@@ -109,10 +111,43 @@ class AppShell extends ConsumerWidget {
     final isRecipesRoute = location.startsWith('/recipes') &&
         !location.startsWith('/recipes/');
     final isImportRoute = location == '/import';
+    final isAdminRoute = location.startsWith('/admin');
+    final adminTab = AdminViewTabX.fromQuery(
+      locationUri.queryParameters['tab'],
+    );
+
+    void navigateToAdminTab(AdminViewTab tab) {
+      final target = '/admin?tab=${tab.queryValue}';
+      if (target != location && context.mounted) {
+        onNavigateToPath(target);
+      }
+    }
+
+    Widget buildAdminTitle() {
+      return SingleChildScrollView(
+        scrollDirection: Axis.horizontal,
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            ChoiceChip(
+              label: const Text('Användare'),
+              selected: adminTab == AdminViewTab.users,
+              onSelected: (_) => navigateToAdminTab(AdminViewTab.users),
+            ),
+            const SizedBox(width: 8),
+            ChoiceChip(
+              label: const Text('Databas'),
+              selected: adminTab == AdminViewTab.database,
+              onSelected: (_) => navigateToAdminTab(AdminViewTab.database),
+            ),
+          ],
+        ),
+      );
+    }
 
     Widget shell = Scaffold(
       appBar: AppBar(
-        title: Text(selectedDestination.title),
+        title: isAdminRoute ? buildAdminTitle() : Text(selectedDestination.title),
         bottom: isImportRoute
             ? const TabBar(
                 tabs: [