The Telegram update dedup cache had a 5-minute TTL which could expire
during extended polling restart cycles (backoff, stall detection, etc.),
allowing already-processed messages to be re-delivered.
- Increase dedup cache TTL from 5 to 30 minutes to survive all realistic
restart windows
- Increase max cache size from 2000 to 5000 to match the longer TTL
- Log a warning when confirmPersistedOffset fails so operators can
diagnose duplicate-message issues
Closes#46674
f4c69a6cfc