fix(test): accept confirm dialog in column reset test

The "Reset Columns to Defaults" test clicked the reset menu item
without handling the browser confirm() dialog. The unhandled dialog
auto-dismissed with cancel, so the reset never executed and the
assertion on default column order failed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: pythoninthegrass

app/frontend/tests/library.spec.js

@@ -2024,6 +2024,8 @@ test.describe('Column Customization', () => {
     expect(albumIdxBefore).toBeLessThan(artistIdxBefore);
 
     // Open context menu and click Reset Columns to Defaults
+    page.on('dialog', dialog => dialog.accept());
+
     const headerRow = page.locator('[data-testid="library-header"]');
     await headerRow.click({ button: 'right' });
     await page.waitForSelector('.header-context-menu', { state: 'visible', timeout: 5000 });