fix(web): keep the reader's locale on the FAQ's internal links

[Lstarsky0]

Summary

The FAQ answers link to /en/install, /en/models, /en/docs/mcp and /en/contribute (and the /zh/ ones in the Chinese answers). Every locale without its own FAQ reads the English answers, so someone on /ja/faq who follows one of those links ends up on the English site. The answers now build these links from the reader's locale, the way the other pages do; #6733 did the same for the constitution page's Install button.

faqEn and faqZh become functions of that prefix, and the page calls the one it picks with it.

No-Issue: small link fix found while moving the site pages off isZh.

Testing

Web only, no Rust touched. From web/:

• npm test — 629 passed
• npm run check — clean

Rendered faq, main vs this branch, all 18 locales: body text, <title>/description/og:/twitter: meta and the FAQPage JSON-LD identical. In en and zh the lang/href attributes are identical too; in the other 16 the only change is those five links moving from /en/… to the reader's locale, and every target page is built for every locale.

Checklist

• This PR adds a new layer/module/abstraction — n/a
• Updated docs or comments as needed — n/a
• Added or updated tests where relevant — n/a
• Verified TUI behavior manually if UI changes — n/a
• Harvested/co-authored credit uses a GitHub numeric noreply address