fix(governance): normalize event and dispatch queries

apps/api/src/services/governance_query_service.py

@@ -85,8 +85,38 @@ def _extract_impact(details: dict) -> str:
     return ""
 
 
+def _extract_remediation(details: dict) -> str | None:
+    """
+    將治理事件 details.remediation 正規化為前端可顯示的短字串。
+
+    Production 事件已出現 dict 形態（例如 {"items": [...]}），API response
+    schema 則是字串。這裡做 read-side normalization，避免歷史資料讓
+    /governance events 變成 500。
+    """
+    remediation = details.get("remediation")
+    if remediation is None:
+        return None
+    if isinstance(remediation, str):
+        return remediation[:160]
+    if isinstance(remediation, dict):
+        for key in ("summary", "message", "reason", "action"):
+            value = remediation.get(key)
+            if isinstance(value, str) and value:
+                return value[:160]
+        items = remediation.get("items")
+        if isinstance(items, list):
+            normalized = [str(item) for item in items if item is not None]
+            if normalized:
+                return "；".join(normalized[:3])[:160]
+        return str(remediation)[:160]
+    if isinstance(remediation, list):
+        normalized = [str(item) for item in remediation if item is not None]
+        return "；".join(normalized[:3])[:160] if normalized else None
+    return str(remediation)[:160]
+
+
 def _to_governance_event(row: AiGovernanceEvent) -> GovernanceEvent:
-    details = row.details or {}
+    details = row.details if isinstance(row.details, dict) else {}
     return GovernanceEvent(
         id=row.id,
         event_type=row.event_type,
@@ -96,7 +126,7 @@ def _to_governance_event(row: AiGovernanceEvent) -> GovernanceEvent:
         resolved_at=row.resolved_at,
         impact=_extract_impact(details),
         details=details,
-        remediation=details.get("remediation"),
+        remediation=_extract_remediation(details),
         dispatch_ids=details.get("dispatch_ids", []),
     )
 
@@ -239,14 +269,14 @@ async def _query_dispatch_table(
             d.dispatch_status,
             d.decision_context,
             d.playbook_id,
-            d.created_at,
+            d.dispatched_at AS created_at,
             d.dispatched_at,
             d.completed_at,
-            d.operator_note
+            NULL::text AS operator_note
         FROM governance_remediation_dispatch d
         JOIN ai_governance_events e ON e.id = d.governance_event_id
         WHERE d.dispatch_status = :dispatch_status
-        ORDER BY d.created_at DESC
+        ORDER BY d.dispatched_at DESC
     """)
 
     count_sql = text("""