feat: add error reporting token validation and update documentation

docs/scheduling.md

@@ -7,6 +7,8 @@ Runs the bot automatically at set times.
 - Turn on scheduling in `src/config.jsonc` under `scheduling.enabled`.
 - Choose a time using the cron or Task Scheduler fields already in the config.
 - Leave the machine or container running so the schedule can trigger.
+- Check the console after start: it prints the next run time. If you close the window or stop the container, the scheduler stops.
+- Serverless hosts (e.g., Vercel) will not keep the scheduler alive; run on a machine or container that stays on.
 
 ## Example
 ```jsonc