feat: add syntax highlighting and enhance document editing features

- Import GitHub dark theme for highlight.js in main.ts
- Pass slug prop to VisualEditor in DocumentView.vue for version and normal editing modes
- Update Vite configuration to increase maximum cache size and add media proxy
- Add new dependencies for Tiptap extensions and highlight.js in package.json and package-lock.json

frontend/vite.config.ts

@@ -25,6 +25,7 @@ export default defineConfig({
         // instead of waiting for all tabs to close.
         skipWaiting: true,
         clientsClaim: true,
+        maximumFileSizeToCacheInBytes: 5000000,
         // Only cache these explicit file types — do NOT cache HTML so the
         // SPA shell is always fetched fresh (prevents stale SW loops).
         globPatterns: ['**/*.{js,css,woff2,png,svg,ico}'],
@@ -50,6 +51,7 @@ export default defineConfig({
     port: 5173,
     proxy: {
       '/graphql': { target: 'http://localhost:4000', changeOrigin: true },
+      '/media': { target: 'http://localhost:4000', changeOrigin: true },
     },
   },
 })