feat: add tags to articles, full i18n coverage, and Tailwind CSS setup

- Add tag frontmatter to all 6 blog articles (3 articles × 2 locales)
- Complete i18n.json with all 26 text keys for en-gb and zh-hans
- Install and configure Tailwind CSS v4 with PostCSS
- Create Tags component using Tailwind utility classes
- Inject Tags into DocLayout via theme override
- Fix zh-hans homepage icon extension

docs/zh-hans/blog/contents/gitlab-ops.md

@@ -1,5 +1,8 @@
 ---
 title: GitLab 运维
+tags:
+  - gitlab
+  - devops
 ---
 
 ## 在国际版 GitLab 中设置默认语言为中文