feat: all-video media row, clickable media selector, download button

- Backend: Add GET /api/games/{id}/download endpoint (ZIP streaming)
- Frontend: All videos now shown in media row alongside screenshots
- Click any media thumbnail to load it into the media container
- Videos show YouTube thumbnail, screenshots show image preview
- Active thumbnail has green border highlight
- Download button between Edit and Delete triggers ZIP download
- Early return: if no media, the entire section is hidden

frontend/src/lib/api.js

@@ -84,6 +84,11 @@ export async function scrapeIGDB(gameId, igdbId) {
   return res.json();
 }
 
+/** Download a game's ZIP bundle */
+export function downloadGame(id) {
+  window.open(`${BASE}/api/games/${id}/download`, '_blank');
+}
+
 /** Check IGDB status */
 export async function igdbStatus() {
   const res = await fetch(`${BASE}/api/igdb/status`);