feat(blog): add city_id to blogs for city-specific scoping

- Introduced a new nullable city_id column in the blogs table to allow scoping of blog posts to specific cities.
- Updated Blog entity to include a ManyToOne relationship with the City entity.
- Enhanced BlogController to handle city_id in the request, allowing filtering of posts by city.
- Modified BlogRepository to support querying published posts based on city_id.
- Added tests to ensure correct behavior for city-scoped and nationwide posts, including creation and updating of posts with city associations.

assets/admin/pages/BlogFormPage.test.tsx

@@ -16,9 +16,13 @@ import { api } from '@/lib/api';
 import BlogFormPage from '@/pages/BlogFormPage';
 
 const post = api.post as ReturnType<typeof vi.fn>;
+const get = api.get as ReturnType<typeof vi.fn>;
 
 beforeEach(() => {
     post.mockReset();
+    // فرم شهرها را برای انتخابگر «سراسری / شهر» می‌گیرد
+    get.mockReset();
+    get.mockResolvedValue({ data: [], meta: { totalRecords: 0, totalPages: 0, currentPage: 1 } });
 });
 
 describe('BlogFormPage — اعتبارسنجی zod (حالت ساخت)', () => {