fix: [FL-195][创建用户报错] 为用户服务事务添加异常处理和回滚机制

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: multica-agent <github@multica.ai>

api/app/services/user_service.py

@@ -114,6 +114,7 @@ def create_user(
         status="ENABLED",
     )
 
+    try:
         db.add(user)
         db.flush()
         _assign_legacy_roles(db, user_id, [])
@@ -128,6 +129,9 @@ def create_user(
             ),
         )
         db.commit()
+    except SQLAlchemyError:
+        db.rollback()
+        return None
 
     created = get_user_by_id(db, user_id)
     if created:
@@ -150,6 +154,7 @@ def delete_user(db: Session, user_id: str, *, actor_user_id: str | None) -> bool
         return False
 
     target_username = user.username
+    try:
         revoke_active_sessions_for_user(db, user_id)
         write_audit_log(
             db,
@@ -162,6 +167,9 @@ def delete_user(db: Session, user_id: str, *, actor_user_id: str | None) -> bool
         )
         db.delete(user)
         db.commit()
+    except SQLAlchemyError:
+        db.rollback()
+        return False
 
     _fire_and_forget(
         publish_topic(
@@ -186,6 +194,7 @@ def reset_user_password(
     if not user:
         return None
 
+    try:
         user.password_hash = hash_password(payload.new_password)
         revoke_active_sessions_for_user(db, user_id)
         write_audit_log(
@@ -200,6 +209,9 @@ def reset_user_password(
             ),
         )
         db.commit()
+    except SQLAlchemyError:
+        db.rollback()
+        return None
 
     updated = get_user_by_id(db, user_id)
     if updated:
@@ -276,6 +288,7 @@ def update_user(
     if not changed_fields:
         return serialize_user(user)
 
+    try:
         write_audit_log(
             db,
             action="user.update",
@@ -292,6 +305,10 @@ def update_user(
             ),
         )
         db.commit()
+    except SQLAlchemyError:
+        db.rollback()
+        return None
+
     updated = get_user_by_id(db, user_id)
     if updated:
         queue_user_auth_refresh(updated, status_changed=status_changed)
@@ -339,6 +356,7 @@ def set_user_roles(
     updated = get_user_by_id(db, user_id)
     if updated:
         authz = get_user_authorization(db, updated.id)
+        try:
             write_audit_log(
                 db,
                 action="user.roles.replace",
@@ -350,6 +368,9 @@ def set_user_roles(
                 ),
             )
             db.commit()
+        except SQLAlchemyError:
+            db.rollback()
+            return None
         queue_user_auth_refresh(updated)
         _fire_and_forget(
             publish_topic(