Remove dead styles from the hub landing page #9066

Task Summary

The hub landing page's stylesheet, frontend/src/app/hub/component/landing-page/landing-page.component.scss, has three rules that match nothing: .search-bar, .section-intro-img and .browse-section. The component uses emulated encapsulation, so they can only match its own template, which uses none of these classes. The browse sections render as <texera-browse-section> elements, which an element selector would match, not the .browse-section class.

Introduced by #2928 (2024-10-29, "Add landing page"), which added all three.

Usage removed by:

• .section-intro-img: fix: restore proper license headers for third-party code #4134 (2026-01-14, "fix: restore proper license headers for third-party code") removed the <img class="section-intro-img"> hub icon.
• .search-bar and .browse-section: never used. No version of the template has had either class.

This is a pure deletion with no behaviour change.

Task Type

• Refactor / Cleanup