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/health_checker.py

@@ -5,11 +5,13 @@ from datetime import datetime
 import httpx
 
 from web.database import SessionLocal
-from web.models import EvotorConnection
+from web.models import EvotorConnection, VkConnection
 
 logger = logging.getLogger("uvicorn.error")
 
 EVOTOR_STORES_URL = "https://api.evotor.ru/stores"
+VK_USERS_GET_URL = "https://api.vk.com/method/users.get"
+VK_API_VERSION = "5.131"
 
 
 async def check_evotor_connection(access_token: str) -> bool:
@@ -25,16 +27,41 @@ async def check_evotor_connection(access_token: str) -> bool:
         return False
 
 
+async def check_vk_connection(access_token: str) -> bool:
+    try:
+        async with httpx.AsyncClient() as client:
+            resp = await client.get(
+                VK_USERS_GET_URL,
+                params={"access_token": access_token, "v": VK_API_VERSION},
+                timeout=10,
+            )
+            if resp.status_code != 200:
+                return False
+            data = resp.json()
+            return "error" not in data
+    except Exception:
+        return False
+
+
 async def run_health_checks() -> None:
     db = SessionLocal()
     try:
-        connections = db.query(EvotorConnection).all()
-        for conn in connections:
-            is_online = await check_evotor_connection(conn.access_token)
-            conn.is_online = is_online
+        evotor_connections = db.query(EvotorConnection).all()
+        for conn in evotor_connections:
+            conn.is_online = await check_evotor_connection(conn.access_token)
             conn.last_checked_at = datetime.utcnow()
+
+        vk_connections = db.query(VkConnection).all()
+        for conn in vk_connections:
+            conn.is_online = await check_vk_connection(conn.access_token)
+            conn.last_checked_at = datetime.utcnow()
+
         db.commit()
-        logger.info("Health checks completed for %d connection(s)", len(connections))
+        logger.info(
+            "Health checks completed: %d Evotor, %d VK",
+            len(evotor_connections),
+            len(vk_connections),
+        )
     except Exception:
         logger.exception("Error during health checks")
         db.rollback()