fix(treatment): open the treatment case when confirming from the panel

confirmWithPayments — the path behind POST /appointment/{uuid}/confirm, which
is how a secretary actually confirms — created the patient session but never
called TreatmentCaseStarter. Only onConfirmed did. So an appointment on a
service with an active protocol was confirmed and paid, and no treatment case
or sessions were ever created; the staff panel had nothing to list.

Every existing test in OpenCaseOnConfirmTest drove onConfirmed, which is why
the gap survived. Added one that drives confirmWithPayments; it fails without
the fix.

Also adds app:treatment:backfill-cases, mirroring
app:appointment:backfill-sessions: it reports confirmed appointments on a
protocol service that have no case, and with --fix replays the starter and
prints the exception the logger would otherwise keep to itself.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/api/appointment.md

@@ -610,6 +610,12 @@ Confirm an appointment («ثبت شده» → «قطعی شده») and register
 case file — status transition, case file / visit, and payments in **one atomic
 transaction**. If any step fails nothing is committed.
 
+> **پروندهٔ درمان هم اینجا باز می‌شود.** اگر سرویسِ نوبت «طول درمان» فعال داشته باشد،
+> همین اندپوینت پروندهٔ چندجلسه‌ای را می‌سازد و نوبت را به اولین جلسهٔ بدون‌نوبت وصل
+> می‌کند — دقیقاً مثل `PATCH /api/v1/appointment/{uuid}/status`.
+> شکستِ این مرحله نوبت و پرداخت را برنمی‌گرداند؛ فقط لاگ می‌شود. پرونده‌های
+> جامانده را `php bin/console app:treatment:backfill-cases --fix` می‌سازد.
+
 **Permission:** `AUTH` — `appointments.update_status` per the
 [single-appointment access model](#single-appointment-access-model).