feat: Add cover art support and auto-migration

- Extract cover art from MP3s during upload
- Display cover art in game result screens (win/loss)
- Add coverImage field to Song model
- Add migration script to backfill covers for existing songs
- Configure Docker to run migration script on startup

Dockerfile

@@ -47,6 +47,7 @@ COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
 COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
 COPY --from=builder --chown=nextjs:nodejs /app/public ./public
 COPY --from=builder --chown=nextjs:nodejs /app/prisma ./prisma
+COPY --from=builder --chown=nextjs:nodejs /app/scripts ./scripts
 
 # Create uploads directory and set permissions
 RUN mkdir -p public/uploads && chown nextjs:nodejs public/uploads