Local analytics with no service behind it

Two tables. activity_event records what happened; event_entity — one row per (event, contributor) — exists only so the "top contributors" query never has to join:

@Entity("activity_event")
data class ActivityEventEntity(
    @PrimaryKey(autoGenerate = true) val eventId: Long = 0,
    val timestamp: LocalDateTime = now(),
    val itemId: String = "", val groupId: String? = null,
    val durationSecond: Long = 0, val listenedSecond: Long = 0,
)