refactor(telegram): migrate alert_routes sender to EventRouter (ADR-019 Phase 5)

routes/alert_routes.py 的 send_telegram_message() 是 Alertmanager webhook 通用告警
出口，原本直接 POST sendMessage 並對每個 chat_id 迴圈。改走 services.event_router.
dispatch_sync() 統一入口（event_type=alertmanager_webhook, severity=alert）。

行為變化：
- 移除手動 chat_id 迴圈，改傳 admin_chat_ids 給 EventRouter（內部仍逐一發）
- 新增 ADR-012 三層分流（L0/L1/L2）+ JSONL queue replay 失敗重送
- parse_mode 參數保留簽名向後相容，但實際統一走 EventRouter HTML 模板
- caller（Alertmanager webhook handler）的 try/except 結構未動

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

routes/alert_routes.py

@@ -96,31 +96,37 @@ def check_alert_auth(f):
 
 
 def send_telegram_message(message: str, parse_mode: str = 'HTML') -> bool:
-    """發送 Telegram 訊息"""
+    """
+    發送 Telegram 訊息
+
+    ADR-019 Phase 5: 改走 EventRouter 統一入口，享 retry + JSONL queue replay。
+    parse_mode 參數保留向後相容（EventRouter 內部統一 HTML，舊 caller 若指定
+    其他 mode 會被忽略；此 route 原本就只用 HTML，影響面=0）。
+    """
     if not TELEGRAM_BOT_TOKEN or not TELEGRAM_CHAT_IDS:
         logger.warning("[Alert] Telegram 未設定，無法發送告警")
         return False
 
-    success = True
-    for chat_id in TELEGRAM_CHAT_IDS:
-        try:
-            url = f"https://api.telegram.org/bot{TELEGRAM_BOT_TOKEN}/sendMessage"
-            payload = {
-                'chat_id': chat_id,
-                'text': message,
-                'parse_mode': parse_mode
-            }
-            response = requests.post(url, json=payload, timeout=10)
-            if response.status_code != 200:
-                logger.error(f"[Alert] Telegram 發送失敗: {response.text}")
-                success = False
-            else:
-                logger.info(f"[Alert] Telegram 訊息已發送到 {chat_id}")
-        except Exception as e:
-            logger.error(f"[Alert] Telegram 發送錯誤: {e}")
-            success = False
-
-    return success
+    try:
+        from services.event_router import dispatch_sync
+        result = dispatch_sync(event={
+            "event_type": "alertmanager_webhook",
+            "severity":   "alert",
+            "source":     "Alertmanager.Webhook",
+            "title":      "Alertmanager 告警",
+            "summary":    message[:400],
+            "status":     "received",
+            "payload":    {"raw_message": message, "parse_mode": parse_mode},
+        }, admin_chat_ids=TELEGRAM_CHAT_IDS)
+        delivered = bool(result.get("delivered"))
+        if not delivered:
+            logger.error(f"[Alert] EventRouter 告警未送達: {result.get('errors')}")
+        else:
+            logger.info(f"[Alert] EventRouter 告警已派送 sent={result.get('sent')}")
+        return delivered
+    except Exception as e:
+        logger.error(f"[Alert] EventRouter dispatch 失敗: {e}")
+        return False
 
 
 def format_alert_message(alert: dict, status: str) -> str: