Add custom error and not found pages, and implement SAML authentication configuration

- Created a new error page (error.twig) with a user-friendly design for displaying error messages.
- Created a new not found page (not-found.twig) to handle 404 errors with appropriate messaging and actions.
- Added a SAML authentication configuration file (settings-custom.php) to support group-based admin assignment and user provisioning.

ots-signs/views/authed.twig

@@ -23,6 +23,17 @@
 {% extends "base.twig" %}
 
 {% block headContent %}
+                {% if not currentUser.isSuperAdmin() and not currentUser.isGroupAdmin() %}
+                <script nonce="{{ cspNonce }}">
+                (function() {
+                    var path = window.location.pathname;
+                    if (path.indexOf('/layout/designer/') !== -1) return;
+                    var cmsIdx = path.toLowerCase().indexOf('/cms');
+                    var portalUrl = window.location.origin + (cmsIdx > 0 ? path.substring(0, cmsIdx) : '') + '/';
+                    window.location.replace(portalUrl);
+                })();
+                </script>
+                {% endif %}
                 <script nonce="{{ cspNonce }}">
                 (function(){
                         try{