feat: add telegram notification channel with outbox service and per-user preferences

Extend the notification system with a third channel (telegram) alongside existing in_app and push channels. Add `telegram_enabled` column to `notification_preferences` table, update `NOTIFICATION_CHANNELS` and `_NOTIFICATION_CHANNEL_COLUMNS` mappings, and set telegram default to off (`_NOTIFICATION_CHANNEL_DEFAULTS`). Create `telegram_outbox` table with columns for uid, user_uid, chat_id, text, status, attempts, created_at, and sent_at, plus an index on status/id for efficient polling. Register `TelegramOutboxService` in the service manager lifecycle. Update API documentation strings to describe the new channel and its pairing requirement. Extend admin notification defaults view to include telegram column. Pass `notif_telegram_paired` flag to profile template based on `telegram_store.is_paired()` check. Update `NotificationPrefForm` and `NotificationDefaultForm` model literals to accept "telegram" as a valid channel value.

devplacepy/services/telegram/bridge.py

@@ -173,6 +173,7 @@ class TelegramBridge:
                     summary=f"Telegram paired for {user.get('username', user['uid'])}",
                     metadata={"chat_id": chat_id},
                 )
+                await self._publish_pairing(user["uid"], True)
                 return
             self._register_attempt(chat_id)
             await self._service.send(chat_id, BAD_CODE)
@@ -198,6 +199,14 @@ class TelegramBridge:
     def _register_attempt(self, chat_id: int) -> None:
         self._attempts.setdefault(chat_id, []).append(time.monotonic())
 
+    async def _publish_pairing(self, user_uid: str, paired: bool) -> None:
+        try:
+            from devplacepy.services.pubsub import publish
+
+            await publish(f"user.{user_uid}.telegram", {"paired": paired})
+        except Exception:  # noqa: BLE001 - live pairing update is best-effort
+            pass
+
     async def _run_turn(
         self, chat_id: int, user: dict[str, Any], text: str, images: list[str]
     ) -> None: