Add Telegram API integration to ava-worker:
- Worker reads TELEGRAM_BOT_TOKEN from env
- On job start: send initial status message, store message_id in subagent_jobs table
- On status change: call editMessageText (with debouncing - max 1 edit per 3s)
- On completion: send final result message
Files: Worker.hs, Jobs.hs (add telegram_message_id column)