chore: remove the remaining VuePress artifacts

Follows the devDependency removal. The build has been mdPress-only since
1.7.0 and nothing referenced these:

- .vuepress/ (config.js + .gitignore). The mirror it configured is still
  live, but no workflow in this repo builds or deploys it, so this was a
  recipe nobody ran. Local .vuepress/dist/ (400 files of Feb-2026 build
  output, never tracked) was removed from the working tree too — with its
  .gitignore gone it would otherwise have shown up as untracked noise.
- docker-compose.yml: the vuepress-offline service, plus the now-unused
  &mdpress-offline anchor that existed only to feed it.
- README: the 'docker run ... :vuepress' one-liner. That tag was last
  pushed 2022-06-25, so readers following it got a four-year-old snapshot
  of the book. 'mdpress serve' immediately above it still works.
- CODEOWNERS, .zhlintignore and check_project_rules.py entries for the
  deleted directory, and the check-link allowlist entry for the mirror
  (no content links to it).

The CHANGELOG entry recording the original CI removal is left alone — it
is history.

Verified: npm test passes (3 + 35), check_project_rules passes 202 files,
docker-compose.yml still parses with no dangling YAML aliases.

.github/CODEOWNERS

@@ -1,7 +1,6 @@
 *                     @yeasy @khs1994
 /.github/*            @khs1994
 /.travis/*            @khs1994
-/.vuepress/*          @khs1994
 /01_introduction/*    @yeasy @khs1994
 /02_basic_concept/*   @yeasy @khs1994
 /03_install/*         @khs1994