feat(api): ADR-038 Circuit Breaker 整合 + Graceful Degradation

sentry_webhook.py:
- 整合 OpenClawGuard (Circuit Breaker + Semaphore)
- 斷路狀態快速失敗，不呼叫 OpenClaw
- 並發控制: 最多 3 個同時 LLM 推理

anomaly_counter.py:
- record_anomaly() Redis 故障 Graceful Degradation
- 失敗時返回預設 AnomalyFrequency (count=0)
- 不中斷主流程

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/services/anomaly_counter.py

@@ -132,14 +132,54 @@ class AnomalyCounter:
         """
         記錄一次異常發生
 
+        ADR-038/039: Redis 故障時 Graceful Degradation
+        - 記錄錯誤但不中斷主流程
+        - 返回空的 AnomalyFrequency（頻率計數 = 0）
+
         Args:
             anomaly_signature: 異常簽名字典
 
         Returns:
-            AnomalyFrequency: 當前頻率統計
+            AnomalyFrequency: 當前頻率統計（Redis 失敗時返回預設值）
         """
         anomaly_key = self.hash_signature(anomaly_signature)
         now = datetime.now()
+
+        try:
+            return await self._record_anomaly_impl(
+                anomaly_key=anomaly_key,
+                anomaly_signature=anomaly_signature,
+                now=now,
+            )
+        except Exception as e:
+            # ADR-038: Redis 故障 Graceful Degradation
+            logger.warning(
+                "anomaly_counter_redis_error",
+                error=str(e),
+                anomaly_key=anomaly_key,
+                fallback="returning_default_frequency",
+            )
+            # 返回預設值，不阻擋主流程
+            return AnomalyFrequency(
+                anomaly_key=anomaly_key,
+                count_1h=0,
+                count_24h=0,
+                count_7d=0,
+                count_30d=0,
+                first_seen=now,
+                last_seen=now,
+                auto_repair_count=0,
+                permanent_fix_applied=False,
+                escalation_level=None,
+            )
+
+    async def _record_anomaly_impl(
+        self,
+        anomaly_key: str,
+        anomaly_signature: dict,
+        now: datetime,
+    ) -> AnomalyFrequency:
+        """實際的異常記錄邏輯（可能拋出 Redis 異常）"""
         timestamp = now.timestamp()
         timeline_key = f"{self.PREFIX_TIMELINE}{anomaly_key}"