feat: add connections dashboard with background health checks

- Add /connections page showing all integrations with online/offline status
- Add background health checker that polls Evotor API every 10 minutes
- Add is_online and last_checked_at fields to evotor_connections table
- Replace Evotor navbar link with unified Connections link
- Redirect connect/disconnect flows to /connections
- Add Alembic migration for new columns

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

web/health_checker.py

@@ -0,0 +1,48 @@
+import asyncio
+import logging
+from datetime import datetime
+
+import httpx
+
+from web.database import SessionLocal
+from web.models import EvotorConnection
+
+logger = logging.getLogger("uvicorn.error")
+
+EVOTOR_STORES_URL = "https://api.evotor.ru/stores"
+
+
+async def check_evotor_connection(access_token: str) -> bool:
+    try:
+        async with httpx.AsyncClient() as client:
+            response = await client.get(
+                EVOTOR_STORES_URL,
+                headers={"Authorization": f"Bearer {access_token}"},
+                timeout=15,
+            )
+            return response.status_code == 200
+    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
+            conn.last_checked_at = datetime.utcnow()
+        db.commit()
+        logger.info("Health checks completed for %d connection(s)", len(connections))
+    except Exception:
+        logger.exception("Error during health checks")
+        db.rollback()
+    finally:
+        db.close()
+
+
+async def health_check_loop(interval: int) -> None:
+    while True:
+        await run_health_checks()
+        await asyncio.sleep(interval)