Avatars are proxied from the slow Habbo upstream on every request
(~350ms each) and Cloudflare was serving them as DYNAMIC because the
Cache-Control had no s-maxage. Add s-maxage=86400 + stale-while-revalidate
so edge/CDN caches avatars and repeats are served instantly.
- Change default public imager URL from habbo.com to /imaging
- /imaging and /api/imaging/avatar now proxy from upstream (habbo.com) instead of redirecting
- Add resolveUpstreamBase() to separate public URL from upstream URL
- Update admin settings default and description