fix(ai-ops): HealLog DetachedInstanceError — refresh before expunge

SQLAlchemy expire_on_commit=True(預設) 會在 commit 後清空 ORM 屬性。
expunge 單獨使用仍會觸發 lazy-load → DetachedInstanceError。
修正：commit → refresh（重載屬性入記憶體）→ expunge（脫離 session）。

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

services/auto_heal_service.py

@@ -373,7 +373,8 @@ class AutoHealService:
             )
             session.add(hl)
             session.commit()
-            session.expunge(hl)  # detach after commit to keep loaded attrs
+            session.refresh(hl)  # reload attrs into memory (expire_on_commit cleared them)
+            session.expunge(hl)  # detach so attrs stay accessible after session.close()
             return hl
         except Exception as e:
             session.rollback()