Replace rollup-plugin-license with rolldown-license-plugin (#37130) (#37158)

Backport #37130. Only one merge conflict in lockfile.

---
This PR was written with the help of Claude Opus 4.6

Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>

tests/e2e/licenses.test.ts

@@ -0,0 +1,9 @@
+import {test, expect} from '@playwright/test';
+
+test('licenses.txt', async ({page}) => {
+  const resp = await page.goto('/assets/licenses.txt');
+  expect(resp?.status()).toBe(200);
+  const content = await resp!.text();
+  expect(content).toContain('@vue/');
+  expect(content).toContain('code.gitea.io/');
+});