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/home.js

@@ -4,7 +4,7 @@ const contentService = require('../services/content');
 
 router.get('/', (req, res) => {
   const homePage = contentService.getPage('/');
-  const recentPosts = contentService.getAllPosts().slice(0, 6);
+  const recentPosts = contentService.getAllPosts().slice(0, 4);
 
   res.render('pages/home', {
     title: homePage ? homePage.title : res.locals.site.title,