fix(web): 本地优先保存与 design 页体验修复

- 保存先写本地缓存，登录后可选云端同步；退出登录不再因文件操作跳转登录

- 修复 Layui 遮罩残留、design2 保存后线条、toast 被 finally 提前关闭

- 保存过程恢复 loading spinner；成功提示 2.5 秒

- 云端 payload 瘦身与体积超限提示；后端 schema 迁移与 FileService 容错

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend-web/js/common/member-activate.js

@@ -79,6 +79,7 @@
       if (idx != null) layer.close(idx);
       if (payIdx != null) layer.close(payIdx);
     }
+    if (typeof window.soonCleanupLayerMask === 'function') window.soonCleanupLayerMask();
     if (fireStay && opts && typeof opts.onStay === 'function') opts.onStay();
   }
 
@@ -93,6 +94,7 @@
     _gate.payIndex = null;
     if (typeof layer !== 'undefined' && gateIdx != null) layer.close(gateIdx);
     _gate = { index: null, payIndex: null, plan: null, gateOpts: null };
+    if (typeof window.soonCleanupLayerMask === 'function') window.soonCleanupLayerMask();
     toast('恭喜您，会员已激活！', 'success');
     if (typeof window.soonLoadMembership === 'function') {
       window.soonLoadMembership(true).then(function () {