fix(telegram): append_incident_update — 儲存告警卡片 message_id 到 Redis

_send_approval_card_to_group 發出告警卡片後，將 Telegram message_id
存入 Redis tg_msg:{incident_id}（TTL 24h），供後續 append_incident_update
換掉批准按鈕 + reply 狀態。

修復前：tg_msg key 從未被寫入，append 永遠 fallback 發新訊息，
批准按鈕永遠無法被移除。

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

apps/api/src/services/telegram_gateway.py

@@ -1577,7 +1577,17 @@ class TelegramGateway:
                 nemotron_latency_ms=nemotron_latency_ms,
             )
             text = message.format_with_nemotron() if nemotron_enabled else message.format()
-            await self.send_to_group(text=text)
+            resp = await self.send_to_group(text=text)
+
+            # 2026-04-10 Claude Sonnet 4.6: 儲存 message_id 到 Redis，供 append_incident_update 使用
+            # tg_msg:{incident_id} → Telegram message_id (TTL 24h)
+            if incident_id and resp:
+                tg_message_id = (resp.get("result") or {}).get("message_id") or resp.get("message_id")
+                if tg_message_id:
+                    from src.core.redis_client import get_redis
+                    redis = get_redis()
+                    await redis.set(f"tg_msg:{incident_id}", str(tg_message_id), ex=86400)
+                    logger.info("tg_msg_id_stored", incident_id=incident_id, message_id=tg_message_id)
         except Exception as e:
             logger.error("send_approval_card_to_group_failed", error=str(e))