fix: standalone start script copies static files automatically

- scripts/start.js: copies .next/static to .next/standalone/.next/static
  before launching the standalone server (prevents CSS 404)
- package.json: start script now uses scripts/start.js
- Dockerfile: removed fragile manual better-sqlite3 copy
  (already included in standalone output)
- scripts/setup.sh: added local prod option for npm start

Dockerfile

@@ -16,13 +16,11 @@ ENV NODE_ENV=production
 RUN addgroup --system --gid 1001 nodejs && \
     adduser --system --uid 1001 nextjs
 
-RUN mkdir -p /app/data/covers && chown -R nextjs:nodejs /app/data
-
 COPY --from=builder /app/public ./public
-RUN mkdir .next
 COPY --from=builder /app/.next/standalone ./
 COPY --from=builder /app/.next/static ./.next/static
-COPY --from=builder /app/node_modules/better-sqlite3 ./node_modules/better-sqlite3
+
+RUN mkdir -p /app/data/covers && chown -R nextjs:nodejs /app/data
 
 USER nextjs
 EXPOSE 3000