chore: fix ruff lint (webhooks v2) + Windows-safe test teardown

app/services/webhook_outbound.py

@@ -112,7 +112,7 @@ def _log_delivery(webhook_id: int, event: str, status: str, http_code: int | Non
 async def _deliver_once(client: httpx.AsyncClient, url: str, event: str,
                          payload: dict, secret: str) -> tuple[int | None, str]:
     """Single POST attempt. Returns (http_code, error).
-    
+
     Includes HMAC-SHA256 signature in X-FlowDeck-Signature header.
     """
     body = json.dumps({"event": event, **payload}).encode()
@@ -144,7 +144,7 @@ async def deliver_to_sub(sub_id: int, url: str, event: str, payload: dict,
 
     Returns True on success. Failures are re-queued via ``next_retry_at`` so
     the background scheduler can pick them up even if this process restarts.
-    
+
     Retry schedule: 2s, 10s, 60s (3 retries total + initial attempt).
     """
     own_client = _client is None