[DT-CMS-2-1] Session & Module Duration Tracking

[sascha11110]

Scope: Store and aggregate session and module duration data (covers categories 2 & 3).

Tasks:

1. Create SessionAggregate model:
   • date (DateField, indexed)
   • total_sessions (IntegerField)
   • total_duration_seconds (BigIntegerField)
   • avg_duration_seconds (IntegerField)
   • duration_buckets (JSONField) - histogram data
2. Create ModuleDurationAggregate model:
   • date (DateField, indexed)
   • exercise_type (IntegerField)
   • unit_id (IntegerField, nullable)
   • total_duration_seconds (BigIntegerField)
   • session_count (IntegerField)
   • avg_duration_seconds (IntegerField)
3. Handle event types: session_start, session_end, module_duration
   • Session payload: { "session_id": string }
   • Module payload: { "exercise_type": number, "unit_id": number | null, "duration_seconds": number }
4. Calculate duration from matching start/end events
5. Create duration histogram buckets: 0-1min, 1-5min, 5-15min, 15-30min, 30min+

Tracking Start (Session): App comes to foreground (AppState = 'active')
Tracking End (Session): App goes to background (AppState = 'background')
Tracking (Module): Single event sent when leaving exercise screen

References:

• AppState hook: lunes-app/src/hooks/useAppState.ts
• Exercise types: lunes-app/src/constants/data.ts

[david-venhoff]

Just wanted to mention that the app cannot guarantee that a session_end event is sent for each session_start event, so this case would need to be handled by the cms