feat: Add Tabs component showcase screen and routing

This commit introduces a new showcase screen for Tabs components, including the necessary routing configuration and theme overrides.

### Key Changes:

*   **Routing & Navigation:**
    *   Defined `tabs` and `tabsUrl` in `RouteNames`.
    *   Added a new `StatefulShellBranch` for the `TabsScreen` in `route_config.dart`.
    *   Added a "Tabs" navigation item to `navigation_items.dart` using the `LucideIcons.appWindow` icon.

*   **UI Components:**
    *   Created `TabsScreen` as a placeholder screen for demonstrating tab components.
    *   Introduced `TabThemes` widget in `tab_themes.dart` to handle tab-specific theme overrides.

*   **Layout:**
    *   Updated `OverrideThemeLayout` to include `TabThemes` in the widget tree, ensuring consistent theme application across the application.

Author: vmeng-b

lib/routes/route_config.dart

@@ -8,6 +8,7 @@ import 'package:police_flutter_template/screens/components/buttons/buttons_scree
 import 'package:police_flutter_template/screens/components/cards/cards_screen.dart';
 import 'package:police_flutter_template/screens/components/forms/forms_screen.dart';
 import 'package:police_flutter_template/screens/components/lists/lists_screen.dart';
+import 'package:police_flutter_template/screens/components/tabs/tabs_screen.dart';
 import 'package:police_flutter_template/screens/error_pages/internal_server_error_screen.dart';
 import 'package:police_flutter_template/screens/error_pages/not_found_screen.dart';
 import 'package:police_flutter_template/screens/home/home_screen.dart';
@@ -215,6 +216,15 @@ class RouteConfig {
                 ),
               ],
             ),
+            StatefulShellBranch(
+              routes: [
+                GoRoute(
+                  name: RouteNames.tabs,
+                  path: RouteNames.tabsUrl,
+                  builder: (context, state) => TabsScreen(),
+                ),
+              ],
+            ),
           ],
         ),
       ],

lib/routes/route_names.dart

@@ -70,4 +70,10 @@ class RouteNames {
 
   /// URL path for the forms demo route (e.g. `/forms`).
   static const String formsUrl = '/$forms';
+
+  /// Route name for the "tabs" component showcase/demo screen.
+  static const String tabs = "tabs";
+
+  /// URL path for the tabs demo route (e.g. `/tabs`).
+  static const String tabsUrl = '/$tabs';
 }

lib/screens/components/tabs/tabs_screen.dart

@@ -0,0 +1,15 @@
+import 'package:shadcn_flutter/shadcn_flutter.dart';
+
+class TabsScreen extends StatefulWidget {
+  const TabsScreen({super.key});
+
+  @override
+  State<TabsScreen> createState() => _TabsScreenState();
+}
+
+class _TabsScreenState extends State<TabsScreen> {
+  @override
+  Widget build(BuildContext context) {
+    return const Placeholder();
+  }
+}

lib/screens/widgets/layouts/override_theme_layout.dart

@@ -4,6 +4,7 @@ import 'package:shadcn_flutter/shadcn_flutter.dart';
 import '../overrides/button_themes.dart';
 import '../overrides/card_themes.dart';
 import '../overrides/container_themes.dart';
+import '../overrides/tab_themes.dart';
 
 class OverrideThemeLayout extends StatelessWidget {
   const OverrideThemeLayout({super.key, required this.child});
@@ -12,9 +13,11 @@ class OverrideThemeLayout extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    return FormThemes(
-      child: ButtonThemes(
-        child: ContainerThemes(child: CardThemes(child: child)),
+    return TabThemes(
+      child: FormThemes(
+        child: ButtonThemes(
+          child: ContainerThemes(child: CardThemes(child: child)),
+        ),
       ),
     );
   }

lib/screens/widgets/overrides/tab_themes.dart

@@ -0,0 +1,13 @@
+import 'package:shadcn_flutter/shadcn_flutter.dart';
+
+
+class TabThemes extends StatelessWidget {
+  const TabThemes({super.key, required this.child});
+
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) {
+    return const Placeholder();
+  }
+}

lib/settings/navigation_items.dart

@@ -98,6 +98,12 @@ class NavigationItems {
           icon: const Icon(LucideIcons.filePenLine),
           onPressed: () => navigationShell.goBranch(5, initialLocation: false),
         ),
+        NavigationItemModel(
+          index: 6,
+          title: "Tabs",
+          icon: const Icon(LucideIcons.appWindow),
+          onPressed: () => navigationShell.goBranch(6, initialLocation: false),
+        ),
         NavigationItemModel(
           index: null,
           title: "404 Nicht gefunden - Standalone",