fix: Telegram 409 감지 시 백오프 대신 polling 즉시 종료 (#180)

409 충돌 감지 시 30초 백오프 후 재시도하는 방식에서
_running = False로 polling을 즉시 중단하는 방식으로 변경.

다중 인스턴스가 실행 중인 경우 재시도는 의미 없고 충돌만 반복됨.
이제 409 발생 시 이 프로세스의 Telegram 명령어 polling을 완전히 비활성화.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/notifications/telegram_client.py

@@ -516,7 +516,6 @@ class TelegramCommandHandler:
         self._last_update_id = 0
         self._polling_task: asyncio.Task[None] | None = None
         self._running = False
-        self._conflict_backoff_until: float = 0.0  # epoch time; skip polling until then
 
     def register_command(
         self, command: str, handler: Callable[[], Awaitable[None]]
@@ -575,12 +574,6 @@ class TelegramCommandHandler:
     async def _poll_loop(self) -> None:
         """Main polling loop that fetches updates."""
         while self._running:
-            # Skip this iteration while a conflict backoff is active
-            now = asyncio.get_event_loop().time()
-            if now < self._conflict_backoff_until:
-                await asyncio.sleep(self._polling_interval)
-                continue
-
             try:
                 updates = await self._get_updates()
                 for update in updates:
@@ -612,15 +605,13 @@ class TelegramCommandHandler:
                 if resp.status != 200:
                     error_text = await resp.text()
                     if resp.status == 409:
-                        # Another bot instance is already polling — back off to reduce conflict.
-                        _conflict_backoff_secs = 30.0
-                        self._conflict_backoff_until = (
-                            asyncio.get_event_loop().time() + _conflict_backoff_secs
-                        )
+                        # Another bot instance is already polling — stop this poller entirely.
+                        # Retrying would keep conflicting with the other instance.
+                        self._running = False
                         logger.warning(
-                            "Telegram conflict (409): another instance is polling. "
-                            "Backing off %.0fs. Ensure only one bot instance runs at a time.",
-                            _conflict_backoff_secs,
+                            "Telegram conflict (409): another instance is already polling. "
+                            "Disabling Telegram commands for this process. "
+                            "Ensure only one instance of The Ouroboros is running at a time.",
                         )
                     else:
                         logger.error(