feat(migration): complete WordPress migration and UX refinements

- Migrate historical posts, localized assets, and 103 comments
- Colocate media into posts/<slug>/images/ and remove wp-content
- Add native bilingual support for ai-can-change post (English default, /zh variant)
- Support clean taxonomy routing (/category/:category and /tag/:tag)
- Dynamically populate categories and tags in sitemap.xml
- Fix header scroll padding/margin offsets for anchor and reference links
- Constrain image and media widths to prevent content overflow
- Redesign homepage recent posts to 4 compact editorial cards
- Restore valid binary favicon.ico and high-res icon assets
- Remove placeholder content and sample test comments

server/routes/post.js

@@ -16,7 +16,7 @@ function renderPost(req, res, next, slug, lang) {
   res.locals.seo = {
     title: `${post.title} - ${res.locals.site.title}`,
     description: post.excerpt || res.locals.site.tagline,
-    canonicalUrl: `${res.locals.site.url}/${post.slug}${post.lang !== 'en' && !post.isDefault ? `/${post.lang}` : ''}`,
+    canonicalUrl: `${res.locals.site.url}/${post.slug}${post.isDefault ? '' : `/${post.lang}`}`,
     ogImage: post.cover ? (post.cover.startsWith('http') ? post.cover : `${res.locals.site.url}${post.cover}`) : res.locals.seo.ogImage,
     type: 'article',
     publishedTime: post.date.toISOString(),
@@ -36,13 +36,22 @@ function renderPost(req, res, next, slug, lang) {
 
 // Route for bilingual variant: /<post-slug>/<lang> (e.g. /my-post/zh)
 router.get('/:slug/:lang([a-zA-Z]{2,5})', (req, res, next) => {
+  const post = contentService.getPost(req.params.slug);
+  if (post && post.defaultLang === req.params.lang) {
+    return res.redirect(301, `/${req.params.slug}`);
+  }
   renderPost(req, res, next, req.params.slug, req.params.lang);
 });
 
+// Legacy redirects for multilingual posts
+router.get('/ai-can-change-coding-for-kids-en', (req, res) => {
+  res.redirect(301, '/ai-can-change-coding-for-kids');
+});
+
 // Route for default language: /<post-slug>
 router.get('/:slug', (req, res, next) => {
   // Exclude reserved top-level prefixes if any
-  const reserved = ['blogs', 'search', 'quick-links', 'feed', 'rss.xml', 'sitemap.xml', 'robots.txt', 'api', 'plugins', 'public', 'posts-assets', 'guanli', 'admin'];
+  const reserved = ['blogs', 'category', 'tag', 'tags', 'search', 'quick-links', 'feed', 'rss.xml', 'sitemap.xml', 'robots.txt', 'api', 'plugins', 'public', 'posts-assets', 'guanli', 'admin'];
   if (reserved.includes(req.params.slug)) {
     return next();
   }