fix(api): 方案 C - Incident 解析相容舊格式 Enum

問題: Redis 存有舊 Enum 值 (status='open', severity='critical')
      導致 Pydantic 驗證失敗

解法:
- normalize_status(): 'open' → 'investigating'
- normalize_severity(): 'critical' → 'P0' 等
- 應用於 get_from_working_memory, get_active_incidents, _record_to_incident

優點:
- 零資料風險 (不動 Redis)
- 回滾 = git revert (秒級)
- 新舊格式都能讀

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

apps/api/src/services/incident_service.py

@@ -35,6 +35,52 @@ from src.models.incident import (
 logger = structlog.get_logger(__name__)
 
 
+# =============================================================================
+# Legacy Value Normalization (方案 C - 代碼相容舊格式)
+# =============================================================================
+# 問題: Redis 有舊 Enum 值 (status='open', severity='critical')
+# 解法: 解析時正規化，不動 Redis 資料
+# 回滾: git revert (秒級恢復)
+# =============================================================================
+
+def normalize_status(value: str) -> str:
+    """
+    正規化 IncidentStatus 舊格式值
+
+    舊值 → 新值:
+    - 'open' → 'investigating'
+    """
+    legacy_map = {
+        "open": "investigating",
+    }
+    return legacy_map.get(value, value)
+
+
+def normalize_severity(value: str) -> str:
+    """
+    正規化 Severity 舊格式值
+
+    舊值 → 新值:
+    - 'critical' → 'P0'
+    - 'high' → 'P1'
+    - 'warning' → 'P2'
+    - 'medium' → 'P2'
+    - 'info' → 'P3'
+    - 'low' → 'P3'
+    - 'none' → 'P3'
+    """
+    legacy_map = {
+        "critical": "P0",
+        "high": "P1",
+        "warning": "P2",
+        "medium": "P2",
+        "info": "P3",
+        "low": "P3",
+        "none": "P3",
+    }
+    return legacy_map.get(value, value)
+
+
 # =============================================================================
 # Constants
 # =============================================================================
@@ -110,6 +156,8 @@ class IncidentService:
         """
         從 Working Memory 讀取 Incident
 
+        方案 C: 解析時正規化舊格式 Enum 值
+
         Returns:
             Incident | None: 事件資料，若不存在則返回 None
         """
@@ -121,7 +169,19 @@ class IncidentService:
             if data is None:
                 return None
 
-            return Incident.model_validate_json(data)
+            # 方案 C: 正規化舊格式 Enum 值
+            incident_dict = json.loads(data)
+            if "status" in incident_dict:
+                incident_dict["status"] = normalize_status(incident_dict["status"])
+            if "severity" in incident_dict:
+                incident_dict["severity"] = normalize_severity(incident_dict["severity"])
+
+            # 同時正規化 signals 內的 severity
+            for signal in incident_dict.get("signals", []):
+                if "severity" in signal:
+                    signal["severity"] = normalize_severity(signal["severity"])
+
+            return Incident.model_validate(incident_dict)
 
         except Exception as e:
             logger.exception(
@@ -131,6 +191,74 @@ class IncidentService:
             )
             return None
 
+    async def get_active_incidents(self) -> list[Incident]:
+        """
+        列出所有活躍的 Incidents (從 Working Memory)
+
+        方案 C: 解析時正規化舊格式 Enum 值
+
+        Returns:
+            list[Incident]: 活躍事件列表 (investigating 或 mitigating)
+        """
+        redis_client = get_redis()
+        incidents: list[Incident] = []
+
+        try:
+            # SCAN 所有 incident:* keys
+            async for key in redis_client.scan_iter(
+                match=f"{INCIDENT_KEY_PREFIX}*",
+                count=100,
+            ):
+                # 排除索引 keys
+                if ":idx:" in key:
+                    continue
+
+                data = await redis_client.get(key)
+                if data is None:
+                    continue
+
+                try:
+                    # 方案 C: 正規化舊格式 Enum 值
+                    incident_dict = json.loads(data)
+                    if "status" in incident_dict:
+                        incident_dict["status"] = normalize_status(incident_dict["status"])
+                    if "severity" in incident_dict:
+                        incident_dict["severity"] = normalize_severity(incident_dict["severity"])
+
+                    # 正規化 signals 內的 severity
+                    for signal in incident_dict.get("signals", []):
+                        if "severity" in signal:
+                            signal["severity"] = normalize_severity(signal["severity"])
+
+                    incident = Incident.model_validate(incident_dict)
+
+                    # 只返回活躍狀態的 Incident
+                    if incident.status in (
+                        IncidentStatus.INVESTIGATING,
+                        IncidentStatus.MITIGATING,
+                    ):
+                        incidents.append(incident)
+                except Exception as e:
+                    logger.warning(
+                        "incident_parse_error",
+                        key=key,
+                        error=str(e),
+                    )
+                    continue
+
+            logger.info(
+                "get_active_incidents",
+                count=len(incidents),
+            )
+            return incidents
+
+        except Exception as e:
+            logger.exception(
+                "get_active_incidents_error",
+                error=str(e),
+            )
+            return []
+
     # =========================================================================
     # Episodic Memory (PostgreSQL)
     # =========================================================================
@@ -225,10 +353,21 @@ class IncidentService:
             return None
 
     def _record_to_incident(self, record: IncidentRecord) -> Incident:
-        """將 SQLAlchemy record 轉換為 Pydantic Incident"""
+        """
+        將 SQLAlchemy record 轉換為 Pydantic Incident
+
+        方案 C: 解析時正規化舊格式 Enum 值
+        """
         from src.models.incident import AIDecisionChain, IncidentOutcome
 
-        signals = [Signal(**s) for s in (record.signals or [])]
+        # 方案 C: 正規化 signals 內的舊格式 severity
+        signals = []
+        for s in (record.signals or []):
+            signal_data = s.copy()
+            if "severity" in signal_data:
+                signal_data["severity"] = normalize_severity(signal_data["severity"])
+            signals.append(Signal(**signal_data))
+
         decision_chain = (
             AIDecisionChain(**record.decision_chain)
             if record.decision_chain
@@ -240,10 +379,14 @@ class IncidentService:
             else None
         )
 
+        # 方案 C: 正規化舊格式 Enum 值
+        normalized_status = normalize_status(record.status)
+        normalized_severity = normalize_severity(record.severity)
+
         return Incident(
             incident_id=record.incident_id,
-            status=IncidentStatus(record.status),
-            severity=Severity(record.severity),
+            status=IncidentStatus(normalized_status),
+            severity=Severity(normalized_severity),
             signals=signals,
             affected_services=record.affected_services or [],
             decision_chain=decision_chain,