feat: improve account deletion and Agent authorization review

apps/api/prisma/migrations/20261004110000_oauth_duration_comment/migration.sql

@@ -0,0 +1 @@
+ALTER TABLE `AgentGrant` MODIFY `refreshExpiresAt` DATETIME(3) NULL COMMENT '刷新授权到期时间，UTC；空表示永久 OAuth 授权或个人令牌不适用';