`try_files` served the SPA fallback inside `location /`, so `/` and every
client route went out without `Cache-Control: no-cache`. The fallback is now
the last argument, an internal redirect to the exact no-cache location.
`src/csp.check.ts` recomputes the inline theme script's sha256 and fails
`bun run check` with the new value when the CSP no longer names it.