refactor: Move settings route outside shell

- Simplify routing structure
- Remove unnecessary nesting

Author: fulleni

lib/router/router.dart

@@ -178,17 +178,13 @@ GoRouter createRouter({
               ),
             ],
           ),
-          StatefulShellBranch(
-            routes: [
-              GoRoute(
-                path: Routes.settings,
-                name: Routes.settingsName,
-                builder: (context, state) => const SettingsPage(),
-              ),
-            ],
-          ),
         ],
       ),
+      GoRoute(
+        path: Routes.settings,
+        name: Routes.settingsName,
+        builder: (context, state) => const SettingsPage(),
+      ),
     ],
   );
 }