[DOCS] Migrate documentation from VuePress 1.x to VitePress (#2299)

- Replace VuePress 1.9.10 with VitePress 1.6.4
- Convert config from CommonJS to ESM TypeScript (config.mts)
- Convert shared Theengs nav config to ESM (commonConfig.mts)
- Rewrite BoardEnvironmentTable in Vue 3 Composition API
- Rewrite FlashEnvironmentSelector in Vue 3 Composition API
- Enable built-in local search and dark mode
- Add medium-zoom for image zoom
- Use VitePress CSS variables for dark mode compatibility
- Update CI script paths from .vuepress to .vitepress
- Update .gitignore for VitePress build artifacts
- Rename README.md files to index.md (VitePress convention)
- Fix markdown compatibility (angle-bracket escaping, image paths)
- Drop PWA plugin (not needed)

Co-authored-by: Florian <1technophile@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -2,19 +2,20 @@
   "scripts": {
     "gen:ssl": "node scripts/ensure_ssl_certs.js",
     "gen:metadata": "node docsgen/gen_wu.js",
-    "gen:site:only": "vuepress build docs",
-    "docs:dev": "npm run gen:metadata && vuepress dev docs",
-    "docs:build": "npm run gen:metadata && npm run gen:site:only",
-    "site:preview": " npm run gen:ssl && node scripts/preview_site.js",
-    "site:preview:full": "npm run docs:build && npm run gen:ssl && node scripts/preview_site.js"
-  },
-  "devDependencies": {
-    "vuepress": "^1.9.10"
+    "gen:commonconfig": "curl -sSf -o docs/.vitepress/public/commonConfig.js https://www.theengs.io/commonConfig.js",
+    "docs:dev": "npm run gen:commonconfig && npm run gen:metadata && vitepress dev docs",
+    "docs:build": "npm run gen:commonconfig && npm run gen:metadata && vitepress build docs",
+    "docs:preview": "vitepress preview docs",
+    "site:preview": " npm run gen:ssl && node scripts/preview_site.js"
   },
   "dependencies": {
     "ini": "^4.1.1",
     "markdown-table": "^3.0.3",
-    "mime-types": "^2.1.35",
-    "vuepress-plugin-sitemap": "^2.3.1"
+    "mime-types": "^2.1.35"
+  },
+  "devDependencies": {
+    "medium-zoom": "^1.1.0",
+    "vitepress": "^1.6.4",
+    "vue": "^3.5.31"
   }
-}
+}