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/en-gb/blog/contents/gitlab-ops.md

@@ -1,5 +1,8 @@
 ---
 title: GitLab Operations
+tags:
+  - gitlab
+  - devops
 ---
 
 ## Setting the Default Language to Chinese in GitLab

docs/en-gb/blog/contents/macos-private-dns-hostname.md

@@ -1,5 +1,9 @@
 ---
 title: Fix macOS Terminal Host Name Showing IP Segments Under Private DNS
+tags:
+  - macos
+  - dns
+  - terminal
 ---
 
 In some enterprise or home private network environments, reverse DNS lookups may resolve a device's private IP to a hostname starting with `192`, `172`, or `10`. When this happens, the macOS terminal prompt changes from the normal `user@MacBook-Pro` to something like `user@192-168-1-100`, which can be distracting.

docs/en-gb/blog/contents/use-of-gravatar.md

@@ -1,5 +1,8 @@
 ---
 title: Use Gravatar in First-party Systems
+tags:
+  - gravatar
+  - avatar
 ---
 
 [Gravatar](https://gravatar.com) (Globally Recognised Avatar) is a service that associates avatar images with email