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>

web/models/connections.py

@@ -81,6 +81,44 @@ class SyncFilter(Base):
     )
 
 
+class VkCachedAlbum(Base):
+    __tablename__ = "vk_cached_albums"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    vk_group_id = Column(String(50), nullable=False)
+    album_id = Column(String(50), nullable=False)
+    title = Column(String(255), nullable=False)
+    count = Column(Integer, nullable=True)
+    fetched_at = Column(DateTime, nullable=False)
+
+    __table_args__ = (
+        UniqueConstraint("user_id", "vk_group_id", "album_id", name="uq_vk_cached_albums"),
+        Index("ix_vk_cached_albums_user_group", "user_id", "vk_group_id"),
+    )
+
+
+class VkCachedProduct(Base):
+    __tablename__ = "vk_cached_products"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    vk_group_id = Column(String(50), nullable=False)
+    vk_product_id = Column(String(50), nullable=False)
+    album_id = Column(String(50), nullable=True)
+    name = Column(String(255), nullable=False)
+    description = Column(Text, nullable=True)
+    price = Column(Numeric(12, 2), nullable=True)
+    availability = Column(Integer, nullable=True)
+    thumb_url = Column(String(1024), nullable=True)
+    fetched_at = Column(DateTime, nullable=False)
+
+    __table_args__ = (
+        UniqueConstraint("user_id", "vk_group_id", "vk_product_id", name="uq_vk_cached_products"),
+        Index("ix_vk_cached_products_user_group_album", "user_id", "vk_group_id", "album_id"),
+    )
+
+
 class CachedStore(Base):
     __tablename__ = "cached_stores"