GET /api/v1/treatment-case/{uuid}/plan returns every session with a date and an
is_estimate flag, plus each session's area records — the device readings a staff
member actually logged. Until now nothing exposed either: due_at existed only
for the next session, and TreatmentCase::toArray() serialised sessions without
their areas, so 'what was done' was unreachable outside the staff panel.
Kept separate from GET /treatment-case/{uuid}; that response feeds the edit
modal, which needs neither the calendar nor the areas.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
