phsl / new-api

Improve UX by hiding the vertical scrollbar inside the announcement (NoticeModal)
while keeping the content scrollable.

Changes
• NoticeModal.js
  - Introduce `notice-content-scroll` class to the content wrapper.
  - Remove inline custom scrollbar styling for cleaner code.

• index.css
  - Add `.notice-content-scroll` to the global hidden-scrollbar rules, ensuring
    scrollbars are hidden across browsers.

Result
Users can still scroll through long announcements, but no scrollbar is shown,
giving the modal a cleaner and more consistent appearance.