Add neutral themes and a public Pages demo

[PeterGuy326]

What changed

• replace the former warm/sage visual theme with Ant Design neutral light and dark palettes
• keep green exclusively for success states and add contrast/legacy-palette regression checks
• add a read-only, sanitized GitHub Pages demo with no backend requests or write operations
• preserve the existing standalone/API-proxy build for local and self-hosted deployments
• document the public demo and add least-privilege Pages deployment automation

Why

The console needed a clear white/dark product theme instead of the green-tinted workspace palette, plus a safe public surface that visitors can explore from the repository without exposing credentials or a live control plane.

Validation

• corepack pnpm test (65 passed, 0 failed, 8 Redis integration tests skipped without the optional URL)
• corepack pnpm --dir admin-dashboard check:design
• corepack pnpm --dir admin-dashboard typecheck
• corepack pnpm --dir admin-dashboard build
• PAGES_BASE_PATH=/waitqueue.js corepack pnpm --dir admin-dashboard build:pages
• corepack pnpm --dir admin-dashboard check:pages
• corepack pnpm --dir admin-dashboard audit --prod --audit-level high
• docker compose config --quiet
• local static subpath asset smoke test and healthy Compose dashboard/API checks