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/api/v1/sentry_webhook.py

@@ -21,6 +21,7 @@ import structlog
 from fastapi import APIRouter, BackgroundTasks, HTTPException, Request
 from pydantic import BaseModel
 
+from src.core.circuit_breaker import get_openclaw_guard
 from src.core.config import settings
 from src.core.metrics import (
     record_alert_chain_failure,
@@ -280,33 +281,52 @@ async def call_openclaw_analyzer(error_context: dict) -> ErrorAnalysisResult | N
     """
     呼叫 OpenClaw Error Analyzer Agent
 
+    ADR-038: 雙層保護
+    - Layer 1: Circuit Breaker（5 連續失敗 → 斷路 60 秒）
+    - Layer 2: Concurrency Semaphore（最多 3 並發）
+
     優先使用 Ollama (本地，零成本)
     Fallback: Claude (高嚴重性)
     """
-    try:
-        async with httpx.AsyncClient(timeout=60.0) as client:
-            response = await client.post(
-                f"{settings.OPENCLAW_URL}/api/v1/analyze/error",
-                json={
-                    "error_context": error_context,
-                    "prefer_local": True,  # 優先 Ollama
-                }
-            )
+    guard = get_openclaw_guard()
 
-            if response.status_code == 200:
-                data = response.json()
-                return ErrorAnalysisResult(**data)
-            else:
-                logger.warning(f"OpenClaw returned {response.status_code}")
-                return None
+    # ADR-038 Layer 1: Circuit Breaker 快速失敗
+    if guard.is_circuit_open():
+        logger.warning(
+            "openclaw_circuit_open",
+            metrics=guard.get_metrics(),
+        )
+        return None
 
-    except httpx.TimeoutException:
-        logger.warning("OpenClaw analysis timeout, trying fallback prompt")
-        # TODO: 直接呼叫 Ollama/Claude 作為 fallback
-        return None
-    except Exception as e:
-        logger.exception(f"OpenClaw call failed: {e}")
-        return None
+    # ADR-038 Layer 2: Concurrency Semaphore 排隊
+    async with guard.semaphore:
+        try:
+            async with httpx.AsyncClient(timeout=60.0) as client:
+                response = await client.post(
+                    f"{settings.OPENCLAW_URL}/api/v1/analyze/error",
+                    json={
+                        "error_context": error_context,
+                        "prefer_local": True,  # 優先 Ollama
+                    }
+                )
+
+                if response.status_code == 200:
+                    data = response.json()
+                    guard.record_success()
+                    return ErrorAnalysisResult(**data)
+                else:
+                    logger.warning(f"OpenClaw returned {response.status_code}")
+                    guard.record_failure()
+                    return None
+
+        except httpx.TimeoutException:
+            logger.warning("OpenClaw analysis timeout")
+            guard.record_failure()
+            return None
+        except Exception as e:
+            logger.exception(f"OpenClaw call failed: {e}")
+            guard.record_failure()
+            return None
 
 
 async def post_sentry_comment(