feat: Update API endpoint usage in repositories to remove redundant path property

- Refactored multiple repository implementations across client and staff features to directly use endpoint objects without accessing the `path` property.
- Introduced a new `FeatureGate` class for client-side feature gating based on user scopes, allowing for better access control to API endpoints.
- Added `ApiEndpoint` class to represent API endpoints with their paths and required scopes for future feature gating.

apps/mobile/packages/features/client/settings/lib/src/data/repositories_impl/settings_repository_impl.dart

@@ -22,7 +22,7 @@ class SettingsRepositoryImpl implements SettingsRepositoryInterface {
   Future<void> signOut() async {
     try {
       // Step 1: Call V2 sign-out endpoint for server-side token revocation.
-      await _apiService.post(AuthEndpoints.clientSignOut.path);
+      await _apiService.post(AuthEndpoints.clientSignOut);
     } catch (e) {
       developer.log(
         'V2 sign-out request failed: $e',