When a Telegram /restart fires and PTB's graceful-shutdown `get_updates`
ACK call times out ("When polling for updates is restarted, updates may
be received twice" in gateway.log), the new gateway receives the same
/restart again and restarts a second time — a self-perpetuating loop.
Record the triggering update_id in `.restart_last_processed.json` when
handling /restart. On the next process, reject a /restart whose
update_id <= the recorded one as a stale redelivery. 5-minute staleness
guard so an orphaned marker can't block a legitimately new /restart.
- gateway/platforms/base.py: add `platform_update_id` to MessageEvent
- gateway/platforms/telegram.py: propagate `update.update_id` through
_build_message_event for text/command/location/media handlers
- gateway/run.py: write dedup marker in _handle_restart_command;
_is_stale_restart_redelivery checks it before processing /restart
- tests/gateway/test_restart_redelivery_dedup.py: 9 new tests covering
fresh restart, redelivery, staleness window, cross-platform,
malformed-marker resilience, and no-update_id (CLI) bypass
Only active for Telegram today (the one platform with monotonic
cross-session update ordering); other platforms return False from
_is_stale_restart_redelivery and proceed normally.
