Refactor application submission response in ApplicationController to return JSON format and update phone number validation rule. Modify careers index view to handle new response structure.

resources/views/web/pages/careers/index.blade.php

@@ -153,7 +153,7 @@
             })
             .then(response => response.json())
             .then(data => {
-                if (data.success) {
+                if (data.message) {
                     alert(data.message);
                     var modal = bootstrap.Modal.getInstance(applicationModal);
                     modal.hide();