🐛 Fixed success state on change password button. (#17410)

closes https://github.com/TryGhost/Product/issues/3604

- The change password button in the user settings wasn't updating correctly.
- the saveNewPasswordTask() wasn't returning anything, causing `
this.get('task.last.value')` to return undefined in the `isSuccess`
method.
- This fix ensures that there is a value attached to the
`task.last.value` so that the condition for a successful save checks
out.

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### <samp>🤖 Generated by Copilot at a6a76eb</samp>

Improved error handling and feedback for changing user passwords in the
settings UI. Modified `saveNewPasswordTask` function in
`ghost/admin/app/controllers/settings/staff/user.js` to catch and
display errors and return user object.

ghost/admin/app/controllers/settings/staff/user.js

@@ -326,8 +326,15 @@ export default class UserController extends Controller {
 
     @task
     *saveNewPasswordTask() {
-        yield this.user.saveNewPasswordTask.perform();
-        document.querySelector('#password-reset')?.reset();
+        try {
+            const user = yield this.user.saveNewPasswordTask.perform();
+            document.querySelector('#password-reset')?.reset();
+            return user;
+        } catch (error) {
+            if (error) {
+                this.notifications.showAPIError(error, {key: 'user.update'});
+            }
+        }
     }
 
     @action