AETHRIX PRODUCTION RECOVERY V4 — 2026-09-06

Fixes aimed at the production failures seen after V3 deployment:
- adds <base href="/"> to all root HTML pages so assets resolve correctly on Cloudflare extensionless URLs;
- versions the redesign CSS/JS to aethrix-redesign-v4.* and cache-busts CSS/JS references;
- adds no-cache static headers during recovery;
- top OS navigation uses /os?direct=1 in production (localhost still uses os.html?direct=1);
- launch actions use /os?boot=1 in production;
- adds explicit /os.html -> /os compatibility redirect;
- keeps Pages Functions routed to /api/* and excludes /assets/*;
- retains functions/api/auth.js and D1 files from the fixed V3 build.