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

src/js/logic/markdown-to-pdf-page.ts

@@ -0,0 +1,21 @@
+import { MarkdownEditor } from '../utils/markdown-editor.js';
+
+document.addEventListener('DOMContentLoaded', () => {
+    const container = document.getElementById('markdown-editor-container');
+
+    if (!container) {
+        console.error('Markdown editor container not found');
+        return;
+    }
+
+    const editor = new MarkdownEditor(container, {});
+
+    console.log('Markdown editor initialized');
+
+    const backButton = document.getElementById('back-to-tools');
+    if (backButton) {
+        backButton.addEventListener('click', () => {
+            window.location.href = '/';
+        });
+    }
+});