重构 monorepo 并完善网页端订阅与首页体验

- 迁移为 frontend-web、frontend-electron、backend-web 与 docker 部署结构
- 网页端：订阅门禁二次弹窗、套餐/支付组件化、顶栏分组对齐
- 首页：最近文件与模板库布局优化，缩略图对齐，下载与删除操作
- 新增管理后台、支付与云端文件 API，更新 README 与项目规范

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

frontend-web/pages/admin/assets/js/components/shell.js

@@ -0,0 +1,40 @@
+(function () {
+  'use strict';
+
+  var I = function () { return window.AdminI18n; };
+
+  function headerHtml(opts) {
+    opts = opts || {};
+    return '<header class="soon-admin-header" id="adminShellHeader">' +
+      '<div class="soon-admin-header__brand">' +
+      '<img class="soon-admin-logo" src="' + I().esc(opts.logoSrc || '../../assets/images/logo.png') + '" alt="">' +
+      '<span>' + I().esc(opts.title || 'SoonDesign Admin') + '</span>' +
+      (opts.env ? '<span class="soon-admin-header__env">' + I().esc(opts.env) + '</span>' : '') +
+      '</div>' +
+      '<div class="soon-admin-header__user">' +
+      (opts.designEntry !== false
+        ? '<a href="' + I().esc(opts.designHref || '../index.web.html') +
+          '" class="soon-btn soon-btn--sm" id="adminDesignEntry" target="_blank" rel="noopener">进入设计端</a>'
+        : '') +
+      '<span id="adminEmail" class="soon-admin-header__email"></span>' +
+      '<button type="button" class="soon-btn soon-btn--ghost soon-btn--sm soon-admin-logout-btn" id="adminLogout">退出</button>' +
+      '</div></header>';
+  }
+
+  function mountHeader(container, opts) {
+    if (!container) return;
+    container.innerHTML = headerHtml(opts);
+  }
+
+  function bindHeader(handlers) {
+    handlers = handlers || {};
+    var logout = document.getElementById('adminLogout');
+    if (logout && handlers.onLogout) logout.onclick = handlers.onLogout;
+  }
+
+  window.AdminShell = {
+    headerHtml: headerHtml,
+    mountHeader: mountHeader,
+    bindHeader: bindHeader,
+  };
+})();