fix(db): prevent double-booking a slot via unique active_slot_key (H2)

A non-unique index on (doctor_id, slot_start) plus a count-then-insert check
left a TOCTOU race: two concurrent requests could both pass isSlotTaken and
both insert. wrapInTransaction alone doesn't stop the phantom under InnoDB
REPEATABLE-READ.

Add a nullable, unique active_slot_key on Appointment = "doctorId:slotStart"
while the booking occupies the slot (pending/confirmed — in lockstep with
isSlotTaken); NULL once expired/completed/no_show/cancelled (NULLs don't collide
in a MySQL unique index, so released slots rebook freely). bookAtomically now:
catches the unique violation -> SlotTakenException, and expires lapsed pendings
in-transaction so the ~1-min window before the expiry cron doesn't wrongly block
rebooking. All three booking paths (online / my / admin) routed through it.

Migration backfills one row per (doctor, slot) — the latest id — so the index
builds even on dirty historical data without destructively cancelling bookings.
(Backfill surfaced a real pre-existing double-booked slot in dev data.)

Regression: tests/Appointment/SlotUniquenessTest. Adjusted the expiry-service
test fixture to use distinct slots (one live booking per slot is now enforced).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/api/appointment.md

@@ -155,6 +155,8 @@ Book an appointment slot.
 
 > **آدرس نوبت:** آدرس (`address_id`) ارسالی نیست؛ سرور آن را از روی `location_id` همان session در برنامه‌ی هفتگی که اسلات در آن قرار دارد، خودکار تعیین و ذخیره می‌کند. در پاسخ به‌صورت `address_id` برمی‌گردد. همه‌ی مسیرهای رزرو (آنلاین `POST /api/v1/appointment`، منشی `POST /api/v1/my/appointment`، ادمین) آدرس را به همین شکل ست می‌کنند.
 
+> **تضمین عدم رزرو دوگانه:** هر سه مسیر رزرو از `AppointmentRepository::bookAtomically()` عبور می‌کنند و یک قید یکتای دیتابیسی (`active_slot_key`) پشت آن قرار دارد؛ بنابراین حتی در شرایط رقابتی (race) فقط یک نوبتِ زنده روی هر `(doctor, slot_start)` ممکن است و درخواست بازنده `409 SLOT_TAKEN` می‌گیرد. نوبت‌های لغو/منقضی اسلات را آزاد می‌کنند (کلید `NULL`).
+
 > **Auto-add to clinic:** هنگام تأیید نوبت، اگر آدرس نوبت متعلق به یک کلینیک باشد (`DoctorAddress.clinic_id`)، بیمار علاوه بر پرونده‌ی پزشک، به پرونده‌های آن کلینیک هم اضافه می‌شود. اگر آدرس کلینیک نداشت ولی دکتر فقط عضو یک کلینیک بود، به همان کلینیک اضافه می‌شود. هر شاخه مشروط به فعال‌بودن `patient_records`. جزئیات در `docs/api/patient.md`.
 
 > **Payer vs patient:** the authenticated user (`user`) is always the payer; the `patient_*` fields describe who the visit is for and are stored separately. **Temporary lock:** the slot is held by the new `pending` booking for **15 minutes** (`expires_at = created_at + 900`). If payment is not completed in time, the booking is moved to `expired` and the slot is freed (see `app:cancel-expired-appointments`). An expired pending booking no longer blocks the slot even before the cron runs.

docs/audit-backlog.md

@@ -38,7 +38,7 @@ _None outstanding._
 | # | Task | File:line | Cat | How to test |
 |---|------|-----------|-----|-------------|
 | ✅H1 | IDOR write: `createAppointment` trusts request `doctor_uuid`, no scope check — any staff books onto any doctor's calendar | src/Appointment/Controller/MyAppointmentsController.php:59 | security-idor | **DONE** — `canBookForDoctor()` scope gate + `tests/Appointment/BookingScopeTest` |
-| H2 | No UNIQUE `(doctor_id, slot_start)` on Appointment → double-booking race (index is non-unique) | src/Appointment/Entity/Appointment.php:13 | db-unique | Concurrent POST same doctor+slot → only one persists. ⚠️ check existing dup data before adding constraint |
+| ✅H2 | No UNIQUE `(doctor_id, slot_start)` on Appointment → double-booking race (index is non-unique) | src/Appointment/Entity/Appointment.php | db-unique | **DONE** — nullable unique `active_slot_key` (occupying = pending/confirmed, mirrors `isSlotTaken`); `bookAtomically` catches the unique violation + expires lapsed pendings in-txn; all 3 booking paths (online/my/admin) routed through it. Migration backfills one row per slot (non-destructive). `tests/Appointment/SlotUniquenessTest`. **NB:** backfill surfaced a real pre-existing double-booked slot in dev data (doctor 1764, two `expired` rows) — harmless (both expired = key NULL). |
 | H3 | `Payment.referenceId` not unique → same gateway callback credited twice | src/Payment/Entity/Payment.php:61-62 | db-unique | Persist two Payments same reference_id → 2nd rejected. (pairs w/ C1) |
 | H4 | `FinancialBreakdown.payment` onDelete CASCADE on non-nullable FK → deleting a Payment destroys ledger rows; should be RESTRICT | src/Settlement/Entity/FinancialBreakdown.php:28-30 | db-ondelete | Delete a Payment w/ breakdown → expect FK restrict error, ledger preserved |
 | H5 | Insurance pricing/coverage modeled as raw int FKs (no FK/onDelete) → orphan rows on delete: `EntityInsurancePricing.entity_id/insurance_id`, `TenantInsurance.entity_id/insurance_id`, `TenantServiceCoverage.tenant_insurance_id` | src/Insurance/Entity/EntityInsurancePricing.php:25-29 · TenantInsurance.php:29,32 · TenantServiceCoverage.php:23-24 | db-ondelete | Delete insurance/tenant → children removed or restricted, no dangling rows |
@@ -105,6 +105,7 @@ _None outstanding._
 | E2 | **No DTO/validator on sensitive writes** — admin create, auth flows, payment verify, booking read raw `json_decode` arrays | Admin, Auth, Payment, Appointment, Settlement controllers | Introduce request DTOs + validator incrementally. Large. |
 | E3 | **Fat controllers** — AdminApiController (1938 LOC), MyAppointmentsController booking, RepresentationActionController (835), DoctorController/ClinicController | extract per-domain Services | SOLID refactor; lower urgency than security/db. |
 | E4 | **CI** — no `.github/workflows`; add phpunit + phpstan + migrate-on-empty-db | devops | prompt var §DevOps |
+| E5 | **phpstan baseline dirty** — 41 pre-existing errors across the codebase (D9 only repaired the config so it *runs*). Audit fixes must not add new ones; cleaning the 41 is its own task. | devops | `ddev exec php vendor/bin/phpstan analyse` → 41 errors (e.g. SlotCalculatorService.php:233, SubscriptionController.php:33) |
 
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