feat: Evotor + VK catalog sync, connections, and store/group filters

- Evotor catalog: background Celery task syncing stores/groups/products
  from Evotor API; UI pages with per-store and per-group sync toggles
- VK connection: manual token + group ID entry with inline test button
- Evotor connection: inline test button (calls /stores)
- VK catalog: background task syncing VK Market albums and products;
  separate catalog UI at /vk-catalog/albums
- SyncFilter extended to support entity_type=group with parent_entity_id
- Migration 0004: vk_cached_albums + vk_cached_products tables
- Beat schedule updated to run both refresh_catalog and refresh_vk_catalog
- README updated with new schema, routes, tasks, and config

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -73,7 +73,7 @@ services:
         condition: service_healthy
       db:
         condition: service_healthy
-    command: celery -A web.tasks.celery_app worker --loglevel=info --concurrency=2 --queues=default,sync,health,notifications
+    command: celery -A web.tasks.celery_app worker --loglevel=info --concurrency=2 --queues=default,sync,health,notifications -E
 
   beat:
     build:
@@ -84,6 +84,7 @@ services:
       DATABASE_URL: mysql+pymysql://${DB_USER}:${DB_PASSWORD}@db:3306/${DB_NAME}
       REDIS_URL: redis://redis:6379/0
       SECRET_KEY: ${SECRET_KEY:-change-me-in-production}
+      CATALOG_REFRESH_INTERVAL_SECONDS: ${CATALOG_REFRESH_INTERVAL_SECONDS:-3600}
     depends_on:
       redis:
         condition: service_healthy