bf53b65706
When `webPassword` is null and the daemon starts headless (systemd, piped
SSH), no longer auto-generate a random password. Instead:
- Boot normally with the gate denying everything except /api/auth/setup
- Panel UI eagerly probes new /api/auth/state on load and renders a
first-run setup overlay (password + confirm) when needsSetup=true
- POST /api/auth/setup writes the chosen password and issues the auth
cookie in the same response, so the operator lands logged in
Interactive TTY behaviour (prompt at the console) is unchanged. The gate
middleware is now registered unconditionally so first-run mode is still
locked-down instead of wide-open.