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/assets/css/tokens.css

@@ -0,0 +1,54 @@
+:root {
+  --soon-bg-deep: #2b3036;
+  --soon-bg-panel: #363d45;
+  --soon-bg-elevated: #3e454d;
+  --soon-bg-content: #31373d;
+  --soon-bg-sidebar: #2f353b;
+  --soon-text: #b8c0c8;
+  --soon-text-muted: #8a939c;
+  --soon-text-strong: #eef1f4;
+  --soon-accent: #009688;
+  --soon-accent-hover: #00a896;
+  --soon-accent-soft: rgba(0, 150, 136, 0.12);
+  --soon-border-subtle: rgba(255, 255, 255, 0.08);
+  --soon-danger: #e57373;
+  --soon-success: #66bb6a;
+  --soon-warning: #ffb74d;
+  --soon-border: #4a525a;
+  --soon-radius: 8px;
+  --soon-radius-sm: 6px;
+  --soon-radius-lg: 10px;
+  --soon-shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
+  --soon-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
+  --soon-ease: cubic-bezier(0.4, 0, 0.2, 1);
+  --soon-font: "Helvetica Neue", Helvetica, Arial, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
+  --soon-font-xs: 12px;
+  --soon-font-sm: 13px;
+  --soon-font-md: 14px;
+  --soon-font-lg: 16px;
+  --soon-btn-h-sm: 32px;
+  --soon-input-h-sm: 36px;
+  --soon-focus-ring: 0 0 0 2px rgba(0, 150, 136, 0.35);
+  --soon-section-gap: 20px;
+  --soon-space-xs: 4px;
+  --soon-space-sm: 8px;
+  --soon-space-md: 16px;
+  --soon-space-lg: 24px;
+  --soon-space-xl: 32px;
+}
+
+@keyframes soon-fadeInUp {
+  from { opacity: 0; transform: translateY(8px); }
+  to { opacity: 1; transform: translateY(0); }
+}
+
+@keyframes soon-shimmer {
+  0% { background-position: -200% 0; }
+  100% { background-position: 200% 0; }
+}
+
+@keyframes soon-shake {
+  0%, 100% { transform: translateX(0); }
+  25% { transform: translateX(-4px); }
+  75% { transform: translateX(4px); }
+}