fix(auth): sync OS login password when the UI password is set at install (#97)

auth.setup only wrote the web password hash to user.json, so the
archipelago system user kept the image default password ("archipelago")
on console/SSH even after the user picked a real password during
onboarding. Reuse the existing usermod-based sync (already used by
auth.changePassword's alsoChangeSsh path) at setup time, best-effort so
a failure can never break onboarding.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/src/api/rpc/auth.rs

@@ -147,6 +147,15 @@ impl RpcHandler {
         self.auth_manager.setup_user(password).await?;
         tracing::info!("[onboarding] user setup complete");
 
+        // The install-time password must also become the OS login for the
+        // archipelago user — otherwise the console/SSH keeps the image default
+        // ("archipelago") after the user has picked a real password (#97).
+        // Best-effort: a failure here must not break onboarding.
+        match crate::auth::change_ssh_password(password).await {
+            Ok(()) => tracing::info!("[onboarding] system login password synced"),
+            Err(e) => tracing::warn!("[onboarding] system login password sync failed: {e}"),
+        }
+
         // Persist the pending onboarding seed as the encrypted backup now that
         // a passphrase (the login password) finally exists — otherwise "Reveal
         // recovery phrase" has nothing to decrypt on this node, ever.