feat: add admin pinned messages section

- API client with full CRUD, broadcast, activate/deactivate, unpin endpoints
- List page with active/inactive badges, action buttons, pagination
- Create/edit form with content editor, media upload, display settings toggles
- Routes and navigation in admin marketing group
- i18n translations for ru, en, fa, zh

src/App.tsx

@@ -73,6 +73,8 @@ const AdminTrafficUsage = lazy(() => import('./pages/AdminTrafficUsage'));
 const AdminUpdates = lazy(() => import('./pages/AdminUpdates'));
 const AdminUserDetail = lazy(() => import('./pages/AdminUserDetail'));
 const AdminBroadcastDetail = lazy(() => import('./pages/AdminBroadcastDetail'));
+const AdminPinnedMessages = lazy(() => import('./pages/AdminPinnedMessages'));
+const AdminPinnedMessageCreate = lazy(() => import('./pages/AdminPinnedMessageCreate'));
 const AdminEmailTemplatePreview = lazy(() => import('./pages/AdminEmailTemplatePreview'));
 
 function ProtectedRoute({ children }: { children: React.ReactNode }) {
@@ -687,6 +689,36 @@ function App() {
             </AdminRoute>
           }
         />
+        <Route
+          path="/admin/pinned-messages"
+          element={
+            <AdminRoute>
+              <LazyPage>
+                <AdminPinnedMessages />
+              </LazyPage>
+            </AdminRoute>
+          }
+        />
+        <Route
+          path="/admin/pinned-messages/create"
+          element={
+            <AdminRoute>
+              <LazyPage>
+                <AdminPinnedMessageCreate />
+              </LazyPage>
+            </AdminRoute>
+          }
+        />
+        <Route
+          path="/admin/pinned-messages/:id/edit"
+          element={
+            <AdminRoute>
+              <LazyPage>
+                <AdminPinnedMessageCreate />
+              </LazyPage>
+            </AdminRoute>
+          }
+        />
         <Route
           path="/admin/email-templates/preview/:type/:lang"
           element={