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/php/router-dev.php

@@ -0,0 +1,31 @@
+<?php
+declare(strict_types=1);
+
+$publicRoot = '/var/www/public';
+$uri = parse_url($_SERVER['REQUEST_URI'] ?? '/', PHP_URL_PATH) ?: '/';
+
+if ($uri === '/health') {
+    header('Content-Type: text/plain; charset=utf-8');
+    echo 'ok';
+    return true;
+}
+
+$file = $publicRoot . $uri;
+if ($uri !== '/' && is_file($file)) {
+    return false;
+}
+
+if (preg_match('#^/api/admin(/.*)?$#', $uri)) {
+    require $publicRoot . '/admin.php';
+    return true;
+}
+
+if (preg_match('#^/api/v1(/.*)?$#', $uri)) {
+    require $publicRoot . '/index.php';
+    return true;
+}
+
+http_response_code(404);
+header('Content-Type: application/json; charset=utf-8');
+echo json_encode(['ok' => false, 'error' => 'not_found', 'message' => 'Not found'], JSON_UNESCAPED_UNICODE);
+return true;