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/pages/admin/assets/js/core/ui.js

@@ -141,10 +141,62 @@
       setBtnLoading(btn, true, opts.loadingLabel);
       ret.finally(function () {
         setBtnLoading(btn, false);
+        if (typeof window.soonCleanupLayerMask === 'function') window.soonCleanupLayerMask();
       });
     }
   }
 
+  function layerContentEl(layero) {
+    if (layero && typeof layero.find === 'function') {
+      return layero.find('.layui-layer-content')[0] || null;
+    }
+    if (layero && layero.querySelector) {
+      return layero.querySelector('.layui-layer-content');
+    }
+    return null;
+  }
+
+  /** 弹窗表单：内容区滚动，保存按钮固定底栏 */
+  function layoutAdminFormModal(contentEl, opts) {
+    if (!contentEl || contentEl.dataset.soonFormLayout) return;
+    opts = opts || {};
+    var root = contentEl.querySelector('.soon-admin-form, .soon-admin-tpl-modal');
+    if (!root) return;
+
+    var foot = root.querySelector('.soon-admin-form__actions, .soon-admin-tpl-modal__actions');
+    if (!foot) {
+      var saveBtn = root.querySelector('#adminModalSave');
+      if (!saveBtn) return;
+      foot = document.createElement('div');
+      foot.className = 'soon-admin-form__actions';
+      saveBtn.parentNode.insertBefore(foot, saveBtn);
+      foot.appendChild(saveBtn);
+    }
+
+    var scroll = document.createElement('div');
+    scroll.className = 'soon-admin-form__scroll';
+    while (root.firstChild && root.firstChild !== foot) {
+      scroll.appendChild(root.firstChild);
+    }
+    if (!scroll.childNodes.length) return;
+
+    root.insertBefore(scroll, foot);
+    root.classList.add('soon-admin-form--modal-shell');
+    foot.classList.add('soon-admin-form__foot');
+
+    contentEl.classList.add('soon-layer-content--form');
+    var area = opts.area || ['420px', 'auto'];
+    if (area[1] && area[1] !== 'auto') {
+      contentEl.classList.add('soon-layer-content--form-fixed');
+      contentEl.style.height = area[1];
+      contentEl.style.maxHeight = area[1];
+    } else if (opts.maxHeight) {
+      contentEl.classList.add('soon-layer-content--form-fixed');
+      contentEl.style.maxHeight = opts.maxHeight;
+    }
+    contentEl.dataset.soonFormLayout = '1';
+  }
+
   function openFormModal(title, formHtml, onSave, opts) {
     if (typeof layer === 'undefined') return;
     opts = opts || {};
@@ -156,16 +208,8 @@
       maxWidth: opts.maxWidth || '96vw',
       content: formHtml,
       success: function (layero) {
-        var area = opts.area || ['420px', 'auto'];
-        if (area[1] && area[1] !== 'auto') {
-          var contentEl = null;
-          if (layero && typeof layero.find === 'function') {
-            contentEl = layero.find('.layui-layer-content')[0];
-          } else if (layero && layero.querySelector) {
-            contentEl = layero.querySelector('.layui-layer-content');
-          }
-          if (contentEl) contentEl.classList.add('soon-layer-content--scroll');
-        }
+        var contentEl = layerContentEl(layero);
+        layoutAdminFormModal(contentEl, opts);
         var btn = document.getElementById('adminModalSave');
         if (btn) {
           btn.onclick = function () {