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>

docker/nginx/frontend.conf

@@ -0,0 +1,29 @@
+server {
+    listen 8080;
+    server_name localhost;
+    root /var/www/web;
+    index pages/index.web.html;
+    charset utf-8;
+    absolute_redirect off;
+    client_max_body_size 32m;
+    location = / { return 302 /pages/index.web.html; }
+    location = /pages { return 302 /pages/index.web.html; }
+    location = /pages/ { return 302 /pages/index.web.html; }
+    location ~* \.(js|css)$ {
+        add_header Cache-Control "no-store, no-cache, must-revalidate";
+        try_files $uri =404;
+    }
+    location / { try_files $uri $uri/ =404; }
+}
+
+server {
+    listen 8081;
+    server_name localhost;
+    root /var/www/electron;
+    index pages/index.html;
+    charset utf-8;
+    absolute_redirect off;
+    client_max_body_size 32m;
+    location = / { return 302 /pages/index.html; }
+    location / { try_files $uri $uri/ =404; }
+}