feat(package): session packages backed by a credit ledger

"Six laser sessions" is the common case in an aesthetics clinic: the patient
pays once and books the sessions later.

Credit is a ledger, not a counter. No table has a remaining/used_count column
and a schema test enforces that — the balance is always SUM(delta) over
append-only rows, so every number a patient sees has a full history behind it.
Corrections are new rows, never edits.

- purchase / consume / refund / adjustment / expiry, each with a reason, an
  author and the appointment it belongs to
- consume happens in confirm(), never in quote(): if the preview consumed, a
  page refresh would cost the patient a session
- cancelling adds a refund row; the consume row stays
- FIFO across a patient's packages — the oldest is closest to expiring
- an empty package is not an error, it just does not apply and the patient pays
- adjust/expire need a doctor or clinic role, and adjust always needs a reason
- app:package:expire writes the closing row so "where did my 3 sessions go?"
  always has an answer

Consume takes a pessimistic lock on the one package row. That is the opposite
of task 07's slot buckets, and docs/api/package.md carries the table explaining
why, so nobody unifies them later.

Idempotency checks for an existing consume row before inserting rather than
catching the unique violation: in Doctrine that exception closes the
EntityManager and burns the rest of the request. The unique key stays as the
last line of defence.

Admin: PackagesPage, a packages tab on the patient record, and a ledger page
whose running-balance column shows where the final number came from.

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

assets/admin/components/layout/SettingsLayout.tsx

@@ -2,7 +2,7 @@ import React from 'react';
 import {
   CreditCardIcon, UserIcon, CalendarDaysIcon, BuildingOffice2Icon,
   BanknotesIcon, UsersIcon, ShieldCheckIcon,
-  TagIcon, ChatBubbleLeftRightIcon, UserCircleIcon, UserPlusIcon, ReceiptPercentIcon, MapPinIcon, CubeIcon, ScaleIcon,
+  TagIcon, ChatBubbleLeftRightIcon, UserCircleIcon, UserPlusIcon, ReceiptPercentIcon, MapPinIcon, CubeIcon, ScaleIcon, RectangleStackIcon,
 } from '@heroicons/react/24/outline';
 import PurchaseSubscriptionSidebar from './PurchaseSubscriptionSidebar';
 
@@ -33,6 +33,7 @@ export const SETTINGS_MENU: SettingsMenuItem[] = [
   { key: 'resources',    label: 'منابع',              icon: CubeIcon,                 to: '/admin/resources',            roles: ['doctor', 'clinic'], perm: ['appointment_settings', 'view'] },
   { key: 'holidays',     label: 'تعطیلات رسمی',       icon: CalendarDaysIcon,         to: '/admin/holidays',             roles: ['doctor', 'clinic'], perm: ['appointment_settings', 'view'] },
   { key: 'policies',     label: 'قوانین',             icon: ScaleIcon,                to: '/admin/policies',             roles: ['doctor', 'clinic'], perm: ['appointment_settings', 'view'] },
+  { key: 'packages',     label: 'پکیج‌ها',            icon: RectangleStackIcon,       to: '/admin/packages',             roles: ['doctor', 'clinic'], perm: ['appointment_settings', 'view'] },
   { key: 'payment',      label: 'مدیریت پرداخت',      icon: BanknotesIcon,            to: '/admin/my-financial',         perm: ['payments', 'view'] },
   { key: 'secretary',    label: 'مدیریت منشی',        icon: UsersIcon,                to: '/admin/my-secretaries' },
   { key: 'staff',        label: 'پرسنل',              icon: UserPlusIcon,             to: '/admin/staff',                perm: ['staff', 'view'] },