Add POST /api/export {projectIds}: one folder per project (named after it),
photos named <lastname-firstname>.<ext>, with a generated initials SVG for
Members without a Slack photo. Dedupe image fetches, bounded concurrency, fflate
zip. Factor data.ts so routes + export share one fixtures/live gating path.
Frontend: Export-photos button downloads the zip.
2b4d056ab8