gateway: add cron finished-run webhook (#14535)

* gateway: add cron finished webhook delivery

* config: allow cron webhook in runtime schema

* cron: require notify flag for webhook posts

* ui/docs: add cron notify toggle and webhook docs

* fix: harden cron webhook auth and fill notify coverage (#14535) (thanks @advaitpaliwal)

---------

Co-authored-by: Tyler Yust <TYTYYUST@YAHOO.COM>

docs/gateway/configuration-reference.md

@@ -2295,12 +2295,16 @@ Current builds no longer include the TCP bridge. Nodes connect over the Gateway
   cron: {
     enabled: true,
     maxConcurrentRuns: 2,
+    webhook: "https://example.invalid/cron-finished", // optional, must be http:// or https://
+    webhookToken: "replace-with-dedicated-token", // optional bearer token for outbound webhook auth
     sessionRetention: "24h", // duration string or false
   },
 }
 ```
 
 - `sessionRetention`: how long to keep completed cron sessions before pruning. Default: `24h`.
+- `webhook`: finished-run webhook endpoint, only used when the job has `notify: true`.
+- `webhookToken`: dedicated bearer token for webhook auth, if omitted no auth header is sent.
 
 See [Cron Jobs](/automation/cron-jobs).