[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>

docsgen/gen_wu.js

@@ -23,9 +23,9 @@ const {
 // Base directories
 const ROOT_DIR = path.join(__dirname, '..');
 const DOCS_DIR = path.join(ROOT_DIR, 'docs');
-const VUEPRESS_DIR = path.join(DOCS_DIR, '.vuepress');
-const PUBLIC_DIR = path.join(VUEPRESS_DIR, 'public');
-const COMPONENTS_DIR = path.join(VUEPRESS_DIR, 'components');
+const VITEPRESS_DIR = path.join(DOCS_DIR, '.vitepress');
+const PUBLIC_DIR = path.join(VITEPRESS_DIR, 'public');
+const COMPONENTS_DIR = path.join(VITEPRESS_DIR, 'components');
 const ARTIFACTS_DIR = path.join(ROOT_DIR, 'generated', 'artifacts');
 
 // Feature-specific directories
@@ -34,8 +34,8 @@ const FIRMWARE_BUILD_DIR = path.join(PUBLIC_DIR, 'firmware_build');
 const BOARDS_INFO_FILE = path.join(PUBLIC_DIR, 'boards-info.json');
 
 // Configuration files
-const DEFAULTS_CONFIG_PATH = path.join(VUEPRESS_DIR, 'defaults.json');
-const META_CONFIG_PATH = path.join(VUEPRESS_DIR, 'meta.json');
+const DEFAULTS_CONFIG_PATH = path.join(VITEPRESS_DIR, 'defaults.json');
+const META_CONFIG_PATH = path.join(VITEPRESS_DIR, 'meta.json');