docs(i18n): 恢复并补齐英文版 vitepress，README 默认改为英文

- README 默认英文：README.en.md → README.md（英文为默认），中文移至 README.zh-CN.md，语言切换链接同步
- 恢复被删除的 docs/en/ 英文文档（git 历史 cc5e53c5^），删除 4 篇已废弃文件
- 英文导航 config.ts 对齐中文结构（新增 Deployment/Changelog 侧栏，同步 Guide/Design 条目）
- 翻译 15 篇中文新增文档：guide 5 篇（certificates/pages-usage/proxy-config/uptime-kuma/zone-domain-migration）+ design 10 篇（zone-design/cloudflare-pointing/waf-orchestration/origin-error-page/edge-cache-design/pages-design/logstore/kuma-design/login-captcha/observability 三篇）
- en 首页更新（新增 Pages 特性、tagline 同步）；changelog 英文入口指向中文版
- vitepress 构建验证：43 个英文页面全部渲染

注意：29 篇旧英文文档为恢复版，部分内容（如 deployment/server、reference/configuration）可能落后于中文，需后续逐篇同步

docs/en/config.ts

@@ -0,0 +1,147 @@
+import { defineAdditionalConfig, type DefaultTheme } from 'vitepress'
+
+export default defineAdditionalConfig({
+  description:
+    'OpenFlare is a lightweight, self-hosted OpenResty control plane for managing reverse proxy rules, configuration publishing, node synchronization, TLS certificates, and basic observability.',
+
+  themeConfig: {
+    nav: nav(),
+
+    sidebar: {
+      '/en/guide/': { base: '/en/guide/', items: sidebarGuide() },
+      '/en/reference/': { base: '/en/reference/', items: sidebarReference() },
+      '/en/deployment/': { base: '/en/deployment/', items: sidebarDeployment() },
+      '/en/design/': { base: '/en/design/', items: sidebarDesign() },
+      '/en/changelog/': { base: '/en/changelog/', items: [] }
+    },
+
+    editLink: {
+      pattern: 'https://github.com/Rain-kl/OpenFlare/edit/main/docs/:path',
+      text: 'Edit this page on GitHub'
+    },
+
+    footer: {
+      message: 'Released under the Apache License 2.0',
+      copyright: 'Copyright © OpenFlare contributors'
+    },
+
+    docFooter: {
+      prev: 'Previous Page',
+      next: 'Next Page'
+    },
+
+    outline: {
+      label: 'On this page'
+    },
+
+    lastUpdated: {
+      text: 'Last updated at'
+    },
+
+    notFound: {
+      title: 'Page Not Found',
+      quote: 'This document does not have a corresponding page yet.',
+      linkLabel: 'Go to Home',
+      linkText: 'Back to OpenFlare Docs'
+    },
+
+    langMenuLabel: 'Language',
+    returnToTopLabel: 'Back to top',
+    sidebarMenuLabel: 'Menu',
+    darkModeSwitchLabel: 'Theme',
+    lightModeSwitchTitle: 'Switch to light theme',
+    darkModeSwitchTitle: 'Switch to dark theme',
+    skipToContentLabel: 'Skip to content'
+  }
+})
+
+function nav(): DefaultTheme.NavItem[] {
+  return [
+    { text: 'Guide', link: '/en/guide/', activeMatch: '/en/guide/' },
+    { text: 'Deployment', link: '/en/deployment/', activeMatch: '/en/deployment/' },
+    { text: 'Reference', link: '/en/reference/', activeMatch: '/en/reference/' },
+    { text: 'Design', link: '/en/design/', activeMatch: '/en/design/' },
+    { text: 'Changelog', link: '/en/changelog/', activeMatch: '/en/changelog/' }
+  ]
+}
+
+function sidebarGuide(): DefaultTheme.SidebarItem[] {
+  return [
+    {
+      text: 'Guide',
+      items: [
+        { text: 'Overview', link: '' },
+        { text: 'Quick Start', link: 'quick-start' },
+        { text: 'TLS Certificates & Auto-Renewal', link: 'certificates' },
+        { text: 'Zone Domain Migration', link: 'zone-domain-migration' },
+        { text: 'Create a Reverse Proxy Config', link: 'proxy-config' },
+        { text: 'Pages Static Hosting Usage', link: 'pages-usage' },
+        { text: 'Tunnel & Intranet Penetration', link: 'tunnel-usage' },
+        { text: 'WAF Security Protection', link: 'waf-usage' },
+        { text: 'WAF Auto IP Group Expressions', link: 'waf-ip-group-expr' },
+        { text: 'Uptime Kuma Monitoring Sync', link: 'uptime-kuma' },
+        { text: 'SSO Login Configuration', link: 'sso' },
+        { text: 'Publish First Configuration', link: 'first-site' },
+        { text: 'Troubleshooting', link: 'troubleshooting' },
+        { text: 'Credits', link: 'credits' }
+      ]
+    }
+  ]
+}
+
+function sidebarReference(): DefaultTheme.SidebarItem[] {
+  return [
+    {
+      text: 'Reference',
+      items: [
+        { text: 'Overview', link: '' },
+        { text: 'Configuration Options', link: 'configuration' },
+        { text: 'CLI Commands', link: 'cli' }
+      ]
+    }
+  ]
+}
+
+function sidebarDeployment(): DefaultTheme.SidebarItem[] {
+  return [
+    {
+      text: 'Deployment',
+      items: [
+        { text: 'Overview', link: '' },
+        { text: 'Deployment Guide', link: 'deployment' },
+        { text: 'Start the Server', link: 'server' },
+        { text: 'Access Agent', link: 'agent' },
+        { text: 'Deploy Relay (Tunnel)', link: 'relay' },
+        { text: 'Deploy OpenFlared', link: 'openflared' },
+        { text: 'Upgrade & Maintenance', link: 'upgrade' }
+      ]
+    }
+  ]
+}
+
+function sidebarDesign(): DefaultTheme.SidebarItem[] {
+  return [
+    {
+      text: 'Design',
+      items: [
+        { text: 'Product Boundaries', link: '' },
+        { text: 'System Architecture', link: 'architecture' },
+        { text: 'Zone & Domain Resource Design', link: 'zone-design' },
+        { text: 'Cloudflare DNS Pointing Design', link: 'cloudflare-pointing' },
+        { text: 'Agent & Publish Model', link: 'agent-design' },
+        { text: 'Tunnel & Intranet Penetration', link: 'tunnel-design' },
+        { text: 'WAF Design', link: 'waf-design' },
+        { text: 'WAF Orchestration Rule Design', link: 'waf-orchestration-design' },
+        { text: 'Pages Static Hosting Design', link: 'pages-design' },
+        { text: 'Edge Cache Strategy Design', link: 'edge-cache-design' },
+        { text: 'Origin Error Page Design', link: 'origin-error-page' },
+        { text: 'Edge Observability & Traffic Stats', link: 'observability-design' },
+        { text: 'Observability Transport Model', link: 'observability-transport-model' },
+        { text: 'Observability Protocol & Tables', link: 'observability-data-model' },
+        { text: 'Log Store Decoupling', link: 'logstore' },
+        { text: 'Uptime Kuma Sync Design', link: 'kuma-design' },
+        { text: 'Login CAPTCHA Design', link: 'login-captcha' }
+      ]
+    }
+  ]
+}