enhance(webhook): add select all and deselect all buttons for custom events (#35980)

Adds `Select All` and `Deselect All` buttons to the custom events
section of the webhook form. This is useful when you need all events but
one.

- The buttons toggle every event checkbox and keep the unsaved-changes
prompt working
- Fix the "Trigger On" radio spacing by removing a leftover Fomantic
checkbox margin

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/e2e/user-settings.test.ts

@@ -1,5 +1,5 @@
 import {test, expect} from '@playwright/test';
-import {loginUser, apiCreateUser, randomString} from './utils.ts';
+import {login, loginUser, apiCreateUser, randomString} from './utils.ts';
 
 test('update profile biography', async ({page, request}) => {
   const username = `e2e-settings-${randomString(8)}`;
@@ -14,3 +14,13 @@ test('update profile biography', async ({page, request}) => {
   await page.getByRole('button', {name: 'Update Profile'}).click();
   await expect(page.getByLabel('Biography')).toHaveValue('');
 });
+
+test('select and deselect all webhook events', async ({page}) => {
+  await login(page);
+  await page.goto('/user/settings/hooks/gitea/new');
+  await page.getByRole('radio', {name: 'Custom Events'}).check();
+  await page.getByRole('button', {name: 'Select All', exact: true}).click();
+  await expect(page.getByRole('checkbox', {checked: false})).toHaveCount(0);
+  await page.getByRole('button', {name: 'Deselect All', exact: true}).click();
+  await expect(page.getByRole('checkbox', {checked: true})).toHaveAccessibleName('Active');
+});