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/migrations/versions/0004_vk_catalog_tables.py

@@ -0,0 +1,56 @@
+"""VK catalog tables (albums + products)
+
+Revision ID: 0004
+Revises: 0003
+Create Date: 2026-05-01
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "0004"
+down_revision: Union[str, None] = "0003"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "vk_cached_albums",
+        sa.Column("id", sa.Integer, primary_key=True, autoincrement=True),
+        sa.Column("user_id", sa.Integer, sa.ForeignKey("users.id", ondelete="CASCADE"), nullable=False),
+        sa.Column("vk_group_id", sa.String(50), nullable=False),
+        sa.Column("album_id", sa.String(50), nullable=False),
+        sa.Column("title", sa.String(255), nullable=False),
+        sa.Column("count", sa.Integer, nullable=True),
+        sa.Column("fetched_at", sa.DateTime, nullable=False),
+        sa.UniqueConstraint("user_id", "vk_group_id", "album_id", name="uq_vk_cached_albums"),
+    )
+    op.create_index("ix_vk_cached_albums_user_group", "vk_cached_albums", ["user_id", "vk_group_id"])
+
+    op.create_table(
+        "vk_cached_products",
+        sa.Column("id", sa.Integer, primary_key=True, autoincrement=True),
+        sa.Column("user_id", sa.Integer, sa.ForeignKey("users.id", ondelete="CASCADE"), nullable=False),
+        sa.Column("vk_group_id", sa.String(50), nullable=False),
+        sa.Column("vk_product_id", sa.String(50), nullable=False),
+        sa.Column("album_id", sa.String(50), nullable=True),
+        sa.Column("name", sa.String(255), nullable=False),
+        sa.Column("description", sa.Text, nullable=True),
+        sa.Column("price", sa.Numeric(12, 2), nullable=True),
+        sa.Column("availability", sa.Integer, nullable=True),
+        sa.Column("thumb_url", sa.String(1024), nullable=True),
+        sa.Column("fetched_at", sa.DateTime, nullable=False),
+        sa.UniqueConstraint("user_id", "vk_group_id", "vk_product_id", name="uq_vk_cached_products"),
+    )
+    op.create_index(
+        "ix_vk_cached_products_user_group_album",
+        "vk_cached_products", ["user_id", "vk_group_id", "album_id"],
+    )
+
+
+def downgrade() -> None:
+    op.drop_table("vk_cached_products")
+    op.drop_table("vk_cached_albums")