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/routes/connections.py

@@ -5,7 +5,7 @@ from sqlalchemy.orm import Session
 
 from web.auth import get_current_user
 from web.database import get_db
-from web.models import User, EvotorConnection
+from web.models import User, EvotorConnection, VkConnection
 
 router = APIRouter()
 templates = Jinja2Templates(directory="web/templates")
@@ -21,6 +21,7 @@ def connections_page(
         return RedirectResponse("/login", 303)
 
     evotor = db.query(EvotorConnection).filter(EvotorConnection.user_id == user.id).first()
+    vk = db.query(VkConnection).filter(VkConnection.user_id == user.id).first()
 
     connections = [
         {
@@ -32,7 +33,17 @@ def connections_page(
             "details": evotor.store_name if evotor else None,
             "connect_url": "/evotor/connect",
             "disconnect_url": "/evotor/disconnect",
-        }
+        },
+        {
+            "name": "ВКонтакте",
+            "icon": "bi-chat-dots",
+            "connected": vk is not None,
+            "is_online": vk.is_online if vk else False,
+            "last_checked_at": vk.last_checked_at if vk else None,
+            "details": f"{vk.first_name} {vk.last_name}".strip() if vk and vk.first_name else None,
+            "connect_url": "/vk",
+            "disconnect_url": "/vk/disconnect",
+        },
     ]
 
     return templates.TemplateResponse("connections.html", {