docs: improve bilingual support for documentation

- Update 404.md with English/Chinese bilingual content
- Update CHANGELOG.md header with bilingual title
- Update ROADMAP.md with bilingual project overview
- Update docs/index.md last updated date to bilingual format

Author: shijiashuai

404.md

@@ -1,32 +1,35 @@
 ---
 layout: default
-title: 404 — 页面未找到
-description: 抱歉，您访问的页面不存在
+title: 404 — Page Not Found
+description: Sorry, the page you are looking for does not exist
 permalink: /404.html
 ---
 
 <div class="page-404">
   <div class="error-code">404</div>
-  <h1 class="error-title">页面未找到</h1>
-  <p class="error-message">抱歉，您访问的页面不存在或已被移动。</p>
-  
+  <h1 class="error-title">Page Not Found / 页面未找到</h1>
+  <p class="error-message">
+    <span>Sorry, the page you are looking for does not exist or has been moved.</span><br>
+    <span style="color: #6c757d;">抱歉，您访问的页面不存在或已被移动。</span>
+  </p>
+
   <div class="error-links">
-    <a href="{{ site.baseurl }}/" class="btn btn-primary">🏠 返回首页</a>
-    <a href="{{ site.baseurl }}/docs/" class="btn">📖 文档中心</a>
-    <a href="https://github.com/LessUp/webrtc" class="btn" target="_blank" rel="noopener">⭐ GitHub 仓库</a>
+    <a href="{{ site.baseurl }}/" class="btn btn-primary">🏠 Home / 首页</a>
+    <a href="{{ site.baseurl }}/docs/" class="btn">📖 Documentation / 文档</a>
+    <a href="https://github.com/LessUp/webrtc" class="btn" target="_blank" rel="noopener">⭐ GitHub</a>
   </div>
-  
+
   <div style="margin-top: 3rem; padding: 1.5rem; background: #f8f9fa; border-radius: 8px; max-width: 500px; margin-left: auto; margin-right: auto;">
-    <h4 style="margin-bottom: 1rem; color: #343a40;">您可能在找：</h4>
+    <h4 style="margin-bottom: 1rem; color: #343a40;">You might be looking for / 您可能在找：</h4>
     <ul style="text-align: left; margin-bottom: 0;">
-      <li><a href="{{ site.baseurl }}/docs/guide">📚 技术指南</a> — 项目整体架构和实现细节</li>
-      <li><a href="{{ site.baseurl }}/docs/signaling">📡 信令协议</a> — WebSocket 消息格式详解</li>
-      <li><a href="{{ site.baseurl }}/docs/deployment">🚀 部署指南</a> — Docker 部署和生产配置</li>
-      <li><a href="{{ site.baseurl }}/CHANGELOG">📝 变更日志</a> — 版本历史和更新记录</li>
+      <li><a href="{{ site.baseurl }}/docs/guide">📚 Technical Guide / 技术指南</a></li>
+      <li><a href="{{ site.baseurl }}/docs/signaling">📡 Signaling Protocol / 信令协议</a></li>
+      <li><a href="{{ site.baseurl }}/docs/deployment">🚀 Deployment Guide / 部署指南</a></li>
+      <li><a href="{{ site.baseurl }}/CHANGELOG">📝 Changelog / 变更日志</a></li>
     </ul>
   </div>
-  
+
   <p style="margin-top: 2rem; color: #6c757d; font-size: 0.9rem;">
-    如果认为这是一个错误，请在 <a href="https://github.com/LessUp/webrtc/issues">GitHub Issues</a> 报告
+    If you believe this is an error, please report it on <a href="https://github.com/LessUp/webrtc/issues">GitHub Issues</a>
   </p>
 </div>

CHANGELOG.md

@@ -1,18 +1,21 @@
 ---
 layout: default
-title: 变更日志 — WebRTC
-description: WebRTC 项目版本历史和变更记录
+title: Changelog — WebRTC
+description: WebRTC version history and release notes - v1.0.0 production release with bilingual documentation
+lang: zh-CN
 ---
 
-[← 返回首页]({{ site.baseurl }}/)
+[← Back to Home]({{ site.baseurl }}/) | [返回首页]({{ site.baseurl }}/)
 
-# 变更日志
+# Changelog / 变更日志
+
+All notable changes are documented in the [`changelog/`](changelog/) directory. This page provides a quick overview of the version history.
 
 所有重要的变更都记录在 [`changelog/`](changelog/) 目录中。本文档提供版本历史的快速概览。
 
 ---
 
-## 版本时间线
+## Version Timeline / 版本时间线
 
 <div class="timeline">
   <div class="timeline-item">

ROADMAP.md

@@ -1,22 +1,26 @@
 ---
 layout: default
-title: 开发路线图 — WebRTC
-description: WebRTC 示例项目各阶段开发计划与进度追踪
+title: Roadmap — WebRTC
+description: WebRTC development roadmap and milestone tracking - features, phases, and future plans
 ---
 
-[← 返回首页]({{ site.baseurl }}/)
+[← Back to Home]({{ site.baseurl }}/) | [返回首页]({{ site.baseurl }}/)
 
-# WebRTC 开发路线图
+# Development Roadmap / 开发路线图
 
-> **项目定位**：基于 Go 的生产级 WebRTC 学习平台，从基础点对点通话到高级多人 Mesh 架构，覆盖 WebRTC 核心能力的完整实现。
+> **Project Positioning / 项目定位**: A production-ready WebRTC learning platform built with Go, covering everything from basic peer-to-peer calls to advanced multi-party Mesh architecture.
+>
+> 基于 Go 的生产级 WebRTC 学习平台，从基础点对点通话到高级多人 Mesh 架构，覆盖 WebRTC 核心能力的完整实现。
+
+This roadmap documents the development plan, milestones, and progress tracking, designed with a progressive learning path.
 
 本路线图记录项目的开发计划、里程碑和进度追踪，采用渐进式学习路径设计。
 
 ---
 
-## 📊 项目概览
+## 📊 Project Overview / 项目概览
 
-### 基本信息
+### Basic Info / 基本信息
 
 | 项目 | 内容 |
 |:-----|:-----|
@@ -294,5 +298,5 @@ description: WebRTC 示例项目各阶段开发计划与进度追踪
 
 ---
 
-**最后更新**：2024-01-15
+**最后更新**：2026-04-17
 **维护者**：LessUp Team

docs/index.md

@@ -1,154 +1,157 @@
 ---
 layout: default
 title: Documentation — WebRTC
-description: 完整的 WebRTC 项目文档，包含技术指南、信令协议、部署说明和故障排除
+description: Complete documentation for WebRTC learning platform - technical guides, signaling protocol, deployment, troubleshooting
 ---
 
 <div class="hero-section" style="padding: 2rem 1rem;">
-  <h1 class="hero-title" style="font-size: 2rem;">📖 文档中心</h1>
-  <p class="hero-subtitle">探索 WebRTC 项目的完整技术文档</p>
+  <h1 class="hero-title" style="font-size: 2rem;">📖 Documentation</h1>
+  <p class="hero-subtitle">
+    <span>Complete technical documentation for WebRTC platform</span><br>
+    <span style="font-size: 0.9rem; color: var(--color-text-light);">WebRTC 项目完整技术文档</span>
+  </p>
 </div>
 
 ---
 
-## 快速导航
+## Quick Navigation
 
 <div class="doc-cards">
   <a href="{{ site.baseurl }}/docs/guide" class="doc-card">
     <span class="doc-icon">🚀</span>
     <div class="doc-content">
-      <h4>快速开始指南</h4>
-      <p>环境准备、本地运行、Docker 部署的最简步骤</p>
+      <h4>Getting Started</h4>
+      <p>Prerequisites, local development, Docker deployment</p>
     </div>
     <span class="doc-arrow">→</span>
   </a>
 
   <a href="{{ site.baseurl }}/docs/signaling" class="doc-card">
     <span class="doc-icon">📡</span>
     <div class="doc-content">
-      <h4>信令协议参考</h4>
-      <p>WebSocket 消息格式、房间管理、心跳机制详解</p>
+      <h4>Signaling Protocol</h4>
+      <p>WebSocket message formats, room management, heartbeat mechanism</p>
     </div>
     <span class="doc-arrow">→</span>
   </a>
 
   <a href="{{ site.baseurl }}/docs/deployment" class="doc-card">
     <span class="doc-icon">🌐</span>
     <div class="doc-content">
-      <h4>生产部署指南</h4>
-      <p>HTTPS/WSS 配置、TURN 服务器、性能优化</p>
+      <h4>Deployment Guide</h4>
+      <p>HTTPS/WSS, TURN server, performance optimization</p>
     </div>
     <span class="doc-arrow">→</span>
   </a>
 
   <a href="{{ site.baseurl }}/docs/troubleshooting" class="doc-card">
     <span class="doc-icon">🔍</span>
     <div class="doc-content">
-      <h4>常见问题排查</h4>
-      <p>连接问题、媒体问题、部署问题的解决方案</p>
+      <h4>Troubleshooting</h4>
+      <p>Connection issues, media problems, deployment solutions</p>
     </div>
     <span class="doc-arrow">→</span>
   </a>
 
   <a href="{{ site.baseurl }}/docs/api" class="doc-card">
     <span class="doc-icon">⚙️</span>
     <div class="doc-content">
-      <h4>API 配置参考</h4>
-      <p>环境变量、端口配置、ICE 服务器配置说明</p>
+      <h4>API Reference</h4>
+      <p>Environment variables, ports, ICE server configuration</p>
     </div>
     <span class="doc-arrow">→</span>
   </a>
 </div>
 
 ---
 
-## 文档结构
+## Documentation Structure
 
-本项目遵循 **Spec-Driven Development (Spec-Driven Development)** 方法论，所有实现都基于规范文档。
+This project follows **Spec-Driven Development (SDD)**. All implementation is driven by specifications.
 
-### 用户与开发者指南
+### User & Developer Guides
 
-| 文档 | 中文 | 英文 | 说明 |
-|:-----|:--:|:--:|:-----|
-| **指南** | [中文](guide.zh-CN.md) | [English](guide.md) | 架构、实现细节、代码走读 |
-| **部署** | [中文](deployment.zh-CN.md) | [English](deployment.md) | Docker、HTTPS/TURN 设置、生产部署 |
-| **信令协议** | [中文](signaling.zh-CN.md) | [English](signaling.md) | WebSocket 协议和消息规范 |
-| **API 参考** | [中文](api.zh-CN.md) | [English](api.md) | 配置选项、环境变量、端点 |
-| **故障排除** | [中文](troubleshooting.zh-CN.md) | [English](troubleshooting.md) | 常见问题和解决方案 |
+| Document | EN | ZH | Description |
+|:---------|:--:|:--:|:------------|
+| **Guide** | [English](guide.md) | [中文](guide.zh-CN.md) | Architecture, implementation details, code walkthrough |
+| **Deployment** | [English](deployment.md) | [中文](deployment.zh-CN.md) | Docker, HTTPS/TURN setup, production deployment |
+| **Signaling** | [English](signaling.md) | [中文](signaling.zh-CN.md) | WebSocket protocol and message specifications |
+| **API Reference** | [English](api.md) | [中文](api.zh-CN.md) | Configuration options, environment variables, endpoints |
+| **Troubleshooting** | [English](troubleshooting.md) | [中文](troubleshooting.zh-CN.md) | Common issues and solutions |
 
-### 规范文档 (Specs)
+### Specification Documents (Single Source of Truth)
 
-规范目录是开发的**单一真相来源 (Single Source of Truth)**：
+The `/specs` directory is the authoritative source. **Specs drive all development.**
 
-| 规范 | 路径 | 说明 |
-|:-----|:-----|:-----|
-| **产品规范** | [`/specs/product/`](../specs/product/) | 功能定义和验收标准 |
-| **RFC 文档** | [`/specs/rfc/`](../specs/rfc/) | 技术设计文档和架构决策 |
-| **API 规范** | [`/specs/api/`](../specs/api/) | OpenAPI 3.0 信令规范 |
-| **数据库规范** | [`/specs/db/`](../specs/db/) | 内存数据结构定义 |
-| **测试规范** | [`/specs/testing/`](../specs/testing/) | BDD 测试规范和验收标准 |
+| Spec | Path | Description |
+|:-----|:-----|:------------|
+| **Product Spec** | [`/specs/product/`](../specs/product/) | Feature definitions and acceptance criteria |
+| **RFC Documents** | [`/specs/rfc/`](../specs/rfc/) | Technical design and architecture decisions |
+| **API Spec** | [`/specs/api/`](../specs/api/) | OpenAPI 3.0 signaling specification |
+| **Database Spec** | [`/specs/db/`](../specs/db/) | In-memory data structure definitions |
+| **Testing Spec** | [`/specs/testing/`](../specs/testing/) | BDD test specifications and acceptance criteria |
 
 ---
 
-## 学习路径
+## Learning Paths
 
-### 🔰 初学者
+### 🔰 Beginners
 
-如果您是 WebRTC 新手，建议按以下顺序阅读：
+If you're new to WebRTC, we recommend reading in this order:
 
-1. **[快速开始指南](guide.md#quick-start)** — 先让项目跑起来
-2. **[信令协议入门](signaling.md#概览)** — 了解浏览器如何建立连接
-3. **[技术指南 - 前端状态机](guide.md#前端状态机)** — 理解客户端如何管理连接状态
+1. **[Getting Started](guide.md#quick-start)** — Get the project running
+2. **[Signaling Protocol Overview](signaling.md#overview)** — Understand how browsers establish connections
+3. **[Frontend State Machine](guide.md#frontend-state-machine)** — Understand client connection state management
 
-### 🛠️ 开发者
+### 🛠️ Developers
 
-如果您想扩展或修改项目：
+If you want to extend or modify the project:
 
-1. **[技术指南 - 架构概览](guide.md#架构概览)** — 整体系统架构
-2. **[RFC-0001: 信令服务器](../specs/rfc/0001-signaling-server.md)** — 服务端设计决策
-3. **[RFC-0002: 前端架构](../specs/rfc/0002-frontend-architecture.md)** — 客户端模块设计
-4. **[产品规范](../specs/product/webrtc-platform.md)** — 功能定义和验收标准
+1. **[Architecture Overview](guide.md#architecture-overview)** — Overall system architecture
+2. **[RFC-0001: Signaling Server](../specs/rfc/0001-signaling-server.md)** — Server design decisions
+3. **[RFC-0002: Frontend Architecture](../specs/rfc/0002-frontend-architecture.md)** — Client module design
+4. **[Product Spec](../specs/product/webrtc-platform.md)** — Feature definitions and acceptance criteria
 
-### 🏭 运维工程师
+### 🏭 DevOps Engineers
 
-如果您需要部署到生产环境：
+If you need to deploy to production:
 
-1. **[部署指南](deployment.md)** — Docker 部署和配置
-2. **[API 配置参考](api.md#configuration)** — 所有环境变量说明
-3. **[故障排除](troubleshooting.md)** — 常见部署问题
+1. **[Deployment Guide](deployment.md)** — Docker deployment and configuration
+2. **[API Configuration Reference](api.md#configuration)** — All environment variables
+3. **[Troubleshooting](troubleshooting.md)** — Common deployment issues
 
 ---
 
-## 相关资源
+## Resources
 
-### 外部链接
+### External Links
 
-| 资源 | 链接 | 说明 |
-|:-----|:-----|:-----|
-| GitHub 仓库 | [LessUp/webrtc](https://github.com/LessUp/webrtc) | 源代码、Issue、PR |
-| 变更日志 | [CHANGELOG.md](../CHANGELOG.md) | 版本历史和发布说明 |
-| 贡献指南 | [CONTRIBUTING.md](../CONTRIBUTING.md) | 开发流程和规范 |
-| 路线图 | [ROADMAP.md](../ROADMAP.md) | 未来开发计划 |
+| Resource | Link | Description |
+|:---------|:-----|:------------|
+| GitHub Repository | [LessUp/webrtc](https://github.com/LessUp/webrtc) | Source code, Issues, PRs |
+| Changelog | [CHANGELOG.md](../CHANGELOG.md) | Version history and release notes |
+| Contributing | [CONTRIBUTING.md](../CONTRIBUTING.md) | Development workflow and guidelines |
+| Roadmap | [ROADMAP.md](../ROADMAP.md) | Future development plans |
 
-### WebRTC 学习资源
+### WebRTC Learning Resources
 
 - [MDN - WebRTC API](https://developer.mozilla.org/en-US/docs/Web/API/WebRTC_API)
-- [WebRTC 官方文档](https://webrtc.org/getting-started/overview)
+- [WebRTC Official Documentation](https://webrtc.org/getting-started/overview)
 - [WebRTC for the Curious](https://webrtcforthecurious.com/)
 
 ---
 
 <div class="callout callout-info">
-  <div class="callout-title">💡 需要帮助？</div>
+  <div class="callout-title">💡 Need Help?</div>
   <ul style="margin-bottom: 0;">
-    <li><strong>发现 Bug？</strong> 在 <a href="https://github.com/LessUp/webrtc/issues">GitHub Issues</a> 提交问题</li>
-    <li><strong>有功能建议？</strong> 查看 <a href="../ROADMAP.md">路线图</a> 或提交 Feature Request</li>
-    <li><strong>想参与贡献？</strong> 阅读 <a href="../CONTRIBUTING.md">贡献指南</a></li>
+    <li><strong>Found a bug?</strong> Open an issue on <a href="https://github.com/LessUp/webrtc/issues">GitHub Issues</a></li>
+    <li><strong>Have a feature request?</strong> Check the <a href="../ROADMAP.md">Roadmap</a> or submit a Feature Request</li>
+    <li><strong>Want to contribute?</strong> Read the <a href="../CONTRIBUTING.md">Contributing Guidelines</a></li>
   </ul>
 </div>
 
 ---
 
-<div style="text-align: center; margin-top: 2rem; color: #6c757d; font-size: 0.9rem;">
-  <strong>最后更新</strong>: 2026-04-17 | <strong>版本</strong>: v1.0.0
+<div style="text-align: center; margin-top: 2rem; color: var(--color-text-light); font-size: 0.9rem;">
+  <strong>Last Updated / 最后更新</strong>: 2026-04-22 | <strong>Version / 版本</strong>: v1.0.0
 </div>