feat(blog): implement tag filtering and facets endpoint

- Fix tag filtering to correctly match Persian tags by adjusting JSON encoding in the applyTagFilter method.
- Add new endpoint GET /api/v1/blogs/tags to retrieve distinct tag names and their counts for published posts, respecting city scope.
- Update API documentation to reflect changes in tag filtering and the new tags endpoint.
- Create BlogTagFilterTest to ensure correct functionality of tag filtering and facets, including edge cases for Persian tags and city filtering.

src/Blog/Controller/BlogController.php

@@ -105,6 +105,51 @@ class BlogController extends BaseController
         return $this->paginated($blogs, $total, $page, $limit);
     }
 
+    #[OA\Get(
+        path: '/api/v1/blogs/tags',
+        summary: 'Distinct tag names of published posts with post counts',
+        parameters: [
+            new OA\Parameter(
+                name: 'city_id',
+                in: 'query',
+                required: false,
+                description: 'Same scope as GET /api/v1/blogs: that city\'s posts plus nationwide posts (city_id IS NULL). Omit to count every published post.',
+                schema: new OA\Schema(type: 'integer')
+            ),
+        ],
+        responses: [
+            new OA\Response(
+                response: 200,
+                description: 'Tag vocabulary of published posts, most used first',
+                content: new OA\JsonContent(
+                    properties: [
+                        new OA\Property(property: 'success', type: 'boolean', example: true),
+                        new OA\Property(
+                            property: 'data',
+                            type: 'array',
+                            items: new OA\Items(
+                                properties: [
+                                    new OA\Property(property: 'name', type: 'string', example: 'چشم و گوش'),
+                                    new OA\Property(property: 'count', type: 'integer', example: 16),
+                                ],
+                                type: 'object'
+                            )
+                        ),
+                    ]
+                )
+            ),
+        ]
+    )]
+    #[Route('/api/v1/blogs/tags', methods: ['GET'])]
+    public function tags(Request $request): JsonResponse
+    {
+        $cityId = $request->query->get('city_id') !== null
+            ? max(1, (int) $request->query->get('city_id'))
+            : null;
+
+        return $this->success($this->blogRepo->tagFacets($cityId));
+    }
+
     #[OA\Get(
         path: '/api/v1/blog/{slug}',
         summary: 'Get a published blog post by slug or UUID',