fix(mysql): read realname policy fallback from im_tenant

Tenant config was merged into im_tenant on the manager side; switch the
DB fallback query accordingly. Keep ErrNoRows/unknown-column fallbacks
so environments before the phase-1 migration degrade to defaults.

server/db/mysql/realname_policy_config.go

@@ -26,6 +26,8 @@ func (a *adapter) RealNamePolicy(tenantID t.TenantID) (*t.RealNamePolicy, error)
 		defer cancel()
 	}
 	var policy t.RealNamePolicy
+	// 商户配置已并入 im_tenant（manager 仓库 im_tenant_merge_config.sql），实名政策兜底直查切到 im_tenant；
+	// id AS tenant_id 保持扫描列名不变，ErrNoRows/未知列仍回退默认值，兼容阶段一迁移未执行的滚动发布窗口
 	err := db.GetContext(ctx, &policy, `SELECT id AS tenant_id, realname_review_policy, realname_provider_mode,
 			realname_required, realname_allow_skip, realname_remind_after
 		FROM im_tenant WHERE id=? LIMIT 1`, tenantID)