feat(catalog): dual durations, item groups, relations and branch overrides

Section 5 of the design document rejects summing service durations. "Face + bikini"
is not 15+12=27 minutes but 15+8=23 — preparation and settling the patient do not
happen twice. Seven wasted minutes times twenty appointments a day is an hour of
capacity lost daily, and AppointmentController was doing exactly that plain sum.

Each item now carries a solo duration and an additional duration. One item counts at
its solo duration and the rest at their additional; the anchor is the item with the
*largest* solo duration rather than the first one selected. Anchoring on selection
order would have let the same basket cost different amounts depending on click order,
so a patient could buy a shorter appointment by reordering. Largest-first is also
conservative: no combination is ever under-estimated, and under-estimating pushes the
next appointment on top of this one.

additional_duration_minutes stays NULL by default and the entity reads NULL as "same
as solo", so every existing service keeps behaving exactly as before — the 236
appointment-domain tests pass unchanged. The old duration_minutes column is kept and
written in step rather than renamed, because other consumers still read it.

ServiceBookingCalculator now delegates to DurationCalculator, which is the one-line
change task 00 predicted when it deliberately preserved the naive sum.

Selection rules are data, not policy: min/max per group is a number, and "bikini does
not combine with full body" is a relation. Putting either in a rules engine means
several rules per service and nobody able to explain a rejection. Validation returns
*all* errors at once rather than the first, since a user with three problems should
not make three round trips. Prerequisite cycles are rejected at write time — storing
both "A requires B" and "B requires A" would make every selection permanently invalid.

Named CatalogCategory, not ServiceCategory: that name is already an insurance enum
(outpatient/inpatient) living on ServiceItem itself, so the two would have collided in
the same file's imports.

Also fixed a defect the tests caught: breakdown() used $overrides[$id]?->… on a key
that may not exist, which warns instead of yielding null.

1175 tests / 3289 assertions. phpstan measured at 14 errors both with and without
this change (verified by stashing). Slot-mode frozen contract green.

The admin UI tab for groups and relations is not built; the checklist records it as
outstanding with a target. The backend is complete and
POST /service-selection/validate is consumable without it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/Shared/Tenant/GlobalTables.php

@@ -104,6 +104,7 @@ final class GlobalTables
         \App\ClinicService\Entity\ServiceItemAuditLog::class   => \App\ClinicService\Entity\ServiceItem::class,
         \App\ClinicService\Entity\ServiceItemConsumable::class => \App\ClinicService\Entity\ServiceItem::class,
         \App\ClinicService\Entity\Tariff::class                => \App\ClinicService\Entity\ServiceItem::class,
+        \App\ClinicService\Entity\ItemGroupMember::class      => \App\ClinicService\Entity\ItemGroup::class,
 
         \App\Billing\Entity\ClaimItem::class      => \App\Billing\Entity\Claim::class,
         \App\Billing\Entity\ClaimStatusLog::class => \App\Billing\Entity\Claim::class,