BE-071: POST /activities/start — begin live activity

Track: 1 — MVP
Section: 1.17 GPS Activity Tracking (Running/Cycling)
Status: [ ] Todo
Repo: backend-api
Branch: feature/BE-071-start-live-activity

Done When

Creates activity with status=in_progress. Returns activity ID. Client sends GPS points to /activities/live

Notes

No notes yet.