Backport from .228 live server:
- AIUI: use SPA fallback (try_files → /aiui/index.html) for client-side routing
- Remove cookie_session gates from AIUI proxies (API key managed by proxy)
- Apply to both HTTP and HTTPS server blocks
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>