永久会员与模板库后台化：预览门控、轻量首页与 Admin CRUD

- 会员改为永久激活方案；云端文件不再拦截非会员；预览弹窗内导出/打印才校验
- 首页最近文件支持本地记录，登录后与云端合并；移除独立会员页与订阅页
- 模板库入库管理：soon_templates 表、Admin 上传 CRUD、/templates 轻量列表与按需下载

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

frontend-web/pages/admin/assets/js/core/router.js

@@ -11,6 +11,7 @@
     '/users': 'users',
     '/orders': 'orders',
     '/plans': 'plans',
+    '/templates': 'templates',
     '/settings': 'settings',
     '/audits': 'audits',
     '/payment': 'payment',
@@ -21,6 +22,7 @@
     users: '/users',
     orders: '/orders',
     plans: '/plans',
+    templates: '/templates',
     settings: '/settings',
     audits: '/audits',
     payment: '/payment',