Adopt @simpleworkjs/frontend's messages/modal/validate modules

Replaces the vendored app.util.actionMessage/actionConfirm/alert (the
latter added ad hoc to fix "app.util.alert is not a function") with the
published @simpleworkjs/frontend package: app.messages.action/confirm,
app.modal.open, and app.validate.js (which also replaces the identical
vendored val.js). Gains real HTML-escaping on message content and a toast
fallback when there's no inline .actionMessage target, neither of which
the vendored code had.

app.api/app.auth/app.pubsub/app.socket in app-base.js are untouched —
they're app-specific (dual-mode callback/promise API, auth-token header
injection) and not something the generic frontend package's app.js
provides, so it isn't loaded here.

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

nodejs/views/impersonate_modal.ejs

@@ -79,7 +79,7 @@ function startImpersonate(uid){
 		$('#impersonateStopBtn').off('click').on('click', function(){
 			app.impersonate.revoke(data.uid, function(err){
 				$('#impersonateModal').modal('hide');
-				if(!err) app.util.actionMessage('Impersonation ended for ' + data.uid, $('body'), 'success');
+				if(!err) app.messages.action('Impersonation ended for ' + data.uid, $('body'), 'success');
 			});
 		});