feat(home): publish the recruitment page and link it from the home entry points

The recruitment page only existed as a theme-dir file, so MkDocs never
published it and nothing could link to it. Serve it from docs/ instead
(MkDocs only copies docs_dir, and extra_templates is docs_dir-scoped too),
then wire it into the nav, the #join-us apply block, and both footer links.

Also fill in applyEmail so the application form actually produces a mailto
target, shorten the EN nav labels and collapse the nav at 1024px so adding
a 7th item does not wrap CJK labels, and teach build_spa.py to rewrite the
new in-site link to an absolute wiki-base URL.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: M09Ic

build_spa.py

@@ -135,6 +135,8 @@ def build(wiki_base: str, out_dir: pathlib.Path, subsets: set, with_fonts: bool)
     # 站内入口: 独立部署时必须是绝对地址
     html = sub(html, 'href="/wiki/"', 'href="%s/"' % wiki_base, expect=1)
     html = sub(html, 'href="/blog/"', 'href="%s/blog/"' % wiki_base, expect=1)
+    html = sub(html, 'href="/recruitment.html"',
+               'href="%s/recruitment.html"' % wiki_base, expect=4)
     # 博客列表: 抓取 wiki 的 blog 索引 (GitHub Pages 返回 access-control-allow-origin: *)
     html = sub(html, "fetch('/blog/')", "fetch('%s/blog/')" % wiki_base, expect=1)
     # 文章链接是相对 blog 索引的, 不能按当前 SPA 的 origin 解析