FCM Service

API-only. No UI. Use the following endpoints:

• POST /notify-workout-log — Notify coach when a client logs a workout (body: { "userId": "<client-uuid>", "logId": "<routine-log-uuid>" })
• POST /notify-client-assigned — Notify coach when a client is assigned to them (body: { "userId": "<client-uuid>" })
• POST /notify-coach-feedback — Notify client when coach leaves feedback (body: { "userId": "<client-uuid>", "logId": "<routine-log-uuid>" })
• POST /notify-incoming-call — Notify callee of incoming call, returns channelName (body: { "calleeUserId", "callerId", "callerName", "callerImageUrl" (optional) })