[Medium] Mobile users can't search #74

Problem

Mobile users can't search.

Root cause

In src/components/layout/Header.tsx:65, the search input is hidden lg:block, so it's hidden on small screens. On mobile there's only a search icon (:68), and it's not a button.

Proposed fix

Make the icon a button that opens a search field.

Acceptance criteria

• On a phone, the user taps the search icon and can search.