fix: copy migration files into Docker runner image for standalone output

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -42,6 +42,7 @@ COPY --from=builder /app/package.json ./package.json
 # https://nextjs.org/docs/advanced-features/output-file-tracing
 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/src/db/migrations ./src/db/migrations
 
 USER nextjs