fix(decision-manager): 修正 CAST 語法 + 關閉 shadow_mode

decision_chain_persist_failed 根因:
  asyncpg 不支援 :dc::json 語法 (:: 與具名參數 : 衝突)
  改為 CAST(:dc AS jsonb) — asyncpg 標準寫法

configmap:
  AIOPS_P4_SHADOW_MODE: true → false
  真實主動監控啟用 (proactive_inspector 輸出供 PreDecisionInvestigator 讀取)

2026-04-16 Claude Sonnet 4.6 Asia/Taipei

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

apps/api/src/services/decision_manager.py

@@ -2344,9 +2344,11 @@ class DecisionManager:
                     existing = []
                 existing.append(entry)
 
+                # asyncpg 不支援 :param::type 語法，改用 CAST(:param AS jsonb)
+                # 2026-04-16 Claude Sonnet 4.6: fix syntax error at or near ":"
                 await db.execute(
                     _sa_text(
-                        "UPDATE incidents SET decision_chain = :dc::json WHERE incident_id = :iid"
+                        "UPDATE incidents SET decision_chain = CAST(:dc AS jsonb) WHERE incident_id = :iid"
                     ),
                     {"dc": _json.dumps(existing), "iid": incident_id},
                 )