feat: add VK OAuth connection with health checks

- Add VkConnection model with is_online/last_checked_at fields
- Add /vk OAuth flow (connect/callback/disconnect/page)
- Add VK entry to connections dashboard
- Extend background health checker to check VK tokens via users.get
- Add Alembic migration for vk_connections table
- Add VK_CLIENT_ID/SECRET/SCOPES/API_VERSION config settings

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

web/main.py

@@ -10,7 +10,7 @@ from web.auth import get_current_user
 from web.config import settings
 from web.health_checker import health_check_loop
 from web.models import User
-from web.routes import auth, profile, reset, evotor
+from web.routes import auth, profile, reset, evotor, vk
 from web.routes import connections
 
 
@@ -35,6 +35,7 @@ app.include_router(profile.router)
 app.include_router(reset.router)
 app.include_router(evotor.router)
 app.include_router(connections.router)
+app.include_router(vk.router)
 
 
 @app.get("/")