Make the selected Unsplash topic chip light green

Switch the active filter chip from dark gray to a light green
background with dark green text.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

components/UnsplashImageSearch.tsx

@@ -176,7 +176,7 @@ export default function UnsplashImageSearch({ onImageSelect, onClose, topic }: U
                   onClick={() => handleQuickSearch(term)}
                   className={`rounded-lg border px-3 py-1.5 text-xs font-medium transition-colors ${
                     active
-                      ? 'border-gray-800 bg-gray-800 text-white'
+                      ? 'border-green-300 bg-green-200 text-green-900'
                       : 'border-gray-200 text-gray-500 hover:bg-gray-50'
                   }`}
                 >