A transient Bot API network error during gateway bootstrap (deleteWebhook
or the initial start_polling) currently raises out of connect() and marks
the Telegram adapter fatal, restart-looping the whole gateway even though
the right behavior is to degrade the Telegram channel and let the existing
reconnect ladder recover in the background.
- _delete_webhook_best_effort(): swallow only transient network errors and
continue to polling; non-network errors (e.g. auth failures) still raise.
- _start_polling_resilient(): on a transient conflict/network error at
bootstrap, schedule background recovery and return degraded instead of
raising; non-transient errors still propagate.
- Track the polling error-callback recovery tasks in _background_tasks so
they can't be garbage-collected mid-flight.
- Add a second Telegram Bot API seed fallback IP (149.154.166.110).
Reconnect keeps its existing 10-retry -> supervisor-restart semantics; this
change only fixes the bootstrap raise, it does not alter the retry ladder.
7a2369718a