✅(frontend) enhance tests

- Removed 'feature/doc-dnd' branch from the Docker Hub workflow to
streamline deployment processes.
- Updated document creation tests to replace 'New page' button
references with 'New doc' for consistency.
- Enhanced test cases to improve clarity and ensure accurate
verification of document functionalities.
- Added new utility function for creating root subpages, improving test
maintainability.

src/frontend/apps/e2e/__tests__/app-impress/doc-search.spec.ts

@@ -154,7 +154,7 @@ test.describe('Sub page search', () => {
       1,
     );
     await verifyDocName(page, doc1Title);
-    await page.getByRole('button', { name: 'New page' }).click();
+    await page.getByRole('button', { name: 'New doc' }).click();
     await verifyDocName(page, '');
     await page.getByRole('textbox', { name: 'doc title input' }).click();
     await page