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.

src/Blog/Repository/BlogRepository.php

@@ -14,9 +14,11 @@ class BlogRepository extends ServiceEntityRepository
     public function findBySlug(string $slug): ?Blog { return $this->findOneBy(['slug' => $slug]); }
 
     /** @return Blog[] published, newest first */
-    public function findPublished(int $page = 1, int $limit = 20, ?string $tag = null): array
+    public function findPublished(int $page = 1, int $limit = 20, ?string $tag = null, ?int $cityId = null): array
     {
         $qb = $this->createQueryBuilder('b')
+            ->leftJoin('b.city', 'c')
+            ->addSelect('c')
             ->where('b.status = :status')
             ->setParameter('status', Blog::STATUS_PUBLISHED)
             ->orderBy('b.createdAt', 'DESC')
@@ -24,11 +26,12 @@ class BlogRepository extends ServiceEntityRepository
             ->setMaxResults($limit);
 
         $this->applyTagFilter($qb, $tag);
+        $this->applyCityFilter($qb, $cityId);
 
         return $qb->getQuery()->getResult();
     }
 
-    public function countPublished(?string $tag = null): int
+    public function countPublished(?string $tag = null, ?int $cityId = null): int
     {
         $qb = $this->createQueryBuilder('b')
             ->select('COUNT(b.id)')
@@ -36,10 +39,26 @@ class BlogRepository extends ServiceEntityRepository
             ->setParameter('status', Blog::STATUS_PUBLISHED);
 
         $this->applyTagFilter($qb, $tag);
+        $this->applyCityFilter($qb, $cityId);
 
         return (int) $qb->getQuery()->getSingleScalarResult();
     }
 
+    /**
+     * دامنهٔ یک شهر باید پست‌های همان شهر **و** پست‌های سراسری را ببیند — پست
+     * سراسری (city NULL) روی همهٔ دامنه‌ها منتشر است، فقط canonicalش روی دامنهٔ اصلی
+     * می‌نشیند. بدون شرط NULL، دامنه‌های شهری محتوای عمومی را از دست می‌دادند.
+     */
+    private function applyCityFilter(\Doctrine\ORM\QueryBuilder $qb, ?int $cityId): void
+    {
+        if ($cityId === null) {
+            return;
+        }
+
+        $qb->andWhere('b.city = :cityId OR b.city IS NULL')
+           ->setParameter('cityId', $cityId);
+    }
+
     private function applyTagFilter(\Doctrine\ORM\QueryBuilder $qb, ?string $tag): void
     {
         if ($tag === null || $tag === '') {