fix(webhooks): 補 get_alert_operation_log_repository import 兩處

alert_received_log_failed 錯誤原因：alertmanager_webhook 函數內
直接呼叫 get_alert_operation_log_repository() 但未在 local scope import，
導致 NameError 被 except 吞掉，ALERT_RECEIVED 事件無法記錄。

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

apps/api/src/api/v1/webhooks.py

@@ -1105,6 +1105,7 @@ async def alertmanager_webhook(
     # Q9: auto_repair flag — Rule=false 強制 HITL（不觸發自動修復背景任務）
     _can_auto_repair_by_rule = _alert_labels.get("auto_repair", "true").lower() == "true"
     try:
+        from src.repositories.alert_operation_log_repository import get_alert_operation_log_repository
         _op_log = get_alert_operation_log_repository()
         await _op_log.append(
             "ALERT_RECEIVED",
@@ -1377,6 +1378,7 @@ async def alertmanager_webhook(
                 )
             else:
                 # auto_repair=false → 記錄 GUARDRAIL_BLOCKED，不觸發自動修復
+                from src.repositories.alert_operation_log_repository import get_alert_operation_log_repository
                 _op_log_rule = get_alert_operation_log_repository()
                 background_tasks.add_task(
                     _op_log_rule.append,