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

.gitignore

@@ -15,4 +15,8 @@ npm-debug.log*
 *.db-journal
 *.db-wal
 *.db-shm
-**/data/*.db*
+**/data/*.db*
+
+# Raw WordPress XML Exports / Backups
+*.WordPress.*.xml
+*.wxr.xml