docs: add english documentation support and internationalization config

1. 新增英文首页文档en/index.md
2. 重构vitepress配置，添加多语言支持，新增英文站点导航与侧边栏
3. 引入mermaid和mathjax3插件支持图表与数学公式

en/index.md

@@ -0,0 +1,38 @@
+---
+layout: home
+
+hero:
+  name: "HF-MES v5.0"
+  text: "MES User Manual"
+  tagline: "Digital Production · Intelligent Execution · Transparent Management"
+  actions:
+    - theme: brand
+      text: Quick Start
+      link: /en/getting-started/quick-start
+    - theme: alt
+      text: System Overview
+      link: /en/guide/system-overview
+
+features:
+  - icon: 🏭
+    title: Production Management
+    details: Comprehensive coverage of production planning, work order execution, and process monitoring
+  - icon: 📊
+    title: Quality Management
+    details: Full-process quality control and traceability from raw materials to finished products
+  - icon: 📦
+    title: Warehouse Logistics
+    details: Optimized inventory management, inbound/outbound processes, and material tracking
+  - icon: 🔧
+    title: Equipment Management
+    details: Complete equipment lifecycle management, inspection, maintenance, and OEE analysis
+  - icon: 🔗
+    title: System Integration
+    details: Seamless integration with ERP, SCADA, and other systems for data connectivity
+  - icon: 📈
+    title: Report Analysis
+    details: Rich statistical analysis reports to support decision-making
+
+footer: |
+  HF-MES v5.0 User Manual · Copyright © 2026 All Rights Reserved
+---