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/deployment/index.md

@@ -0,0 +1,24 @@
+# Deployment & Upgrade
+
+This section provides detailed deployment guides, configuration instructions, and upgrade maintenance procedures for the OpenFlare Server, Agent, Relay, and the OpenFlared client.
+
+## Content Navigation
+
+### Quick Start
+* **[Quick Start](../guide/quick-start.md)**: Start the Server and your first Agent in under 5 minutes using Docker Compose (recommended for new users).
+
+### Server Deployment
+* **[Launch Server](./server.md)**: Learn how to build the frontend from source, start the Server, and choose between SQLite or PostgreSQL.
+
+### Agent Deployment
+* **[Deploy Agent](./agent.md)**: Explore Agent connection methods, Docker deployment, host script installation, config files, and troubleshooting.
+
+### Tunnel Intranet Penetration Deployment
+* **[Deploy Relay](./relay.md)**: View config descriptions, Docker deployment, and host runtime guides for TunnelRelay nodes.
+* **[Deploy OpenFlared](./openflared.md)**: Access config descriptions, Docker runtime, and auto-sync mechanisms for the intranet client.
+
+### Upgrade & Maintenance
+* **[Upgrade & Maintenance](./upgrade.md)**: Discover upgrading procedures for Server/Agent, data retention rules, and validation commands.
+
+### Reference Manuals
+* **[Deployment Guide](./deployment.md)**: Browse deployment topologies, prerequisites, Docker Compose samples, and multiple deployment strategies.