feat(gui): close a modal when pressing ESC after switching modal tabs (fixes #9489) (#10092)

### Purpose

As stated in #9489 after clicking on a tab link to switch tabs in a
modal you can no longer close the modal through clicking the ESC key
unless you click anywhere on the modal to focus on it again.

### Testing

- Click on a modal that has tabs like "Settings" or "Add Folder" and
switch tabs then click on ESC.
- Check if clicking outside of a modal in the backdrop should still
close the modal.

### Demo


https://github.com/user-attachments/assets/a010db9a-72f7-4160-a7db-ddfebffb4834

gui/default/syncthing/core/modalDirective.js

@@ -16,6 +16,14 @@ angular.module('syncthing.core')
             },
             link: function (scope, element, attrs) {
 
+                $(element).on('click', function (event) {
+                    const closestTabAnchor = event.target.closest('a[data-toggle="tab"]');
+
+                    if (closestTabAnchor && closestTabAnchor.href.includes('#')) {
+                        event.preventDefault();
+                    }
+                });
+
                 // before modal show animation
                 $(element).on('show.bs.modal', function () {