Multi-stage build: node builds the SPA, dotnet publishes the API, the
runtime image serves the SPA from wwwroot/ and exposes /health. Frontend
Supabase URL + publishable key are baked in at build time; DB conn string
and Supabase JWKS metadata come from Coolify env vars. VITE_API_URL empty
means same-origin, so the browser hits /api/todos on the same host that
serves the SPA.
The scaffolded template shipped an opinionated marketing-page CSS
(fixed #root width, large h1 sizes, letter-spacing) that made the
TodoList header overlap. Replaced with a minimal reset so component
inline styles render as intended.
