feat(backend): watches report alert counts, alerts carry watch params and time away, webhooks their last delivery

backend/src/api/routers/webhooks.py

@@ -61,13 +61,16 @@ async def list_webhooks(
 async def create_webhook(
     pool: FromDishka[asyncpg.Pool], body: WebhookCreate
 ) -> WebhookView:
-    return await webhooks.create_webhook(
+    webhook = await webhooks.create_webhook(
         pool,
         body.account_id,
         _url(body.url),
         _watch_ids(body.watch_ids),
         enabled=body.enabled,
     )
+    if webhook is None:
+        raise HTTPException(status_code=500, detail="webhook was not saved")
+    return webhook
 
 
 @router.put("/{webhook_id}")