fix: address final review findings

- CRITICAL: Add binaries and .svelte-kit/ to .gitignore, remove from tracking
- HIGH: Return error from computeExpectedFQDNs to prevent mass DNS
  deletion on transient DB errors during sync
- MEDIUM: Log error in rollback DNS cleanup when GetSettings fails

internal/deployer/rollback.go

@@ -46,8 +46,10 @@ func (d *Deployer) rollback(ctx context.Context, deployID string, containerID st
 	if instanceID != "" {
 		inst, err := d.store.GetInstanceByID(instanceID)
 		if err == nil && inst.Subdomain != "" {
-			settings, _ := d.store.GetSettings()
-			if settings.Domain != "" {
+			settings, settingsErr := d.store.GetSettings()
+			if settingsErr != nil {
+				slog.Warn("rollback: failed to get settings for DNS cleanup", "error", settingsErr)
+			} else if settings.Domain != "" {
 				fqdn := inst.Subdomain + "." + settings.Domain
 				d.removeDNS(ctx, fqdn, deployID)
 			}