feat: Add VitePress docs, EPUB to PDF tool, Phosphor icons, and licensing updates

- Set up VitePress documentation site (docs:dev, docs:build, docs:preview)
- Added Getting Started, Tools Reference, Contributing, and Commercial License pages
- Created self-hosting guides for Docker, Vercel, Netlify, Cloudflare, AWS, Hostinger, Nginx, Apache
- Updated README with documentation link, sponsors section, and docs contribution guide

- Added EPUB to PDF converter using LibreOffice WASM

- Migrated to Phosphor Icons for consistent iconography

- Added donation ribbon banner on landing page
- Removed 'Like My Work?' section (replaced by ribbon)
- Updated licensing.html with delivery model, AGPL notice, invoicing, and no-refund policy

- Added Commercial License documentation page
- Updated translations table (Chinese added, marked non-English as In Progress)

- Added sponsors.yml workflow for auto-generating sponsor avatars

public/locales/zh/common.json

@@ -53,7 +53,8 @@
         "toolsLabel": "工具",
         "subtitle": "点击工具以打开文件上传",
         "searchPlaceholder": "搜索工具 (例如 '合并', '分割'...)",
-        "backToTools": "返回工具列表"
+        "backToTools": "返回工具列表",
+        "firstLoadNotice": "首次加载需要一点时间，因为我们正在下载转换引擎。之后所有加载将即时完成。"
     },
     "upload": {
         "clickToSelect": "点击选择文件",