Add Access group admin surfaces, booking soft deletes, refund crash fix

Access group (Filament):
- StaffResource: manage users with an admin-tier role, gated by manage_staff
- CustomerResource: read-only view of role-less users, gated by view_customers
- RoleResource: edit permissions per role (fixed role set), gated by manage_roles
- ManageAppSettings: tabbed General/Booking settings page that reads/writes
  real .env keys via new EnvFileWriter (no parallel DB settings table, so
  BookingService/config('booking.*') stay unchanged)
- Moved Access above Catalog in the nav group order
- New permissions: manage_staff, manage_roles, view_customers, manage_settings

Booking soft deletes:
- bookings.deleted_at + SoftDeletes on the Booking model
- BookingPolicy::delete (manage_bookings, cancelled/expired only) and
  ::restore (manage_bookings)
- DeleteBookingTableAction/RestoreBookingTableAction + TrashedFilter on
  BookingsTable, using authorize() so the policy is enforced at call time,
  not just cosmetically hidden

Refund crash fix:
- ProcessRefundAction passed a nullable $payment->booking into
  RefundBookingAction's non-nullable Booking param — a soft-deleted
  booking's payment reaching the refund picker was an uncaught TypeError.
  Excluded such payments from the picker and added a defensive guard.
- Same unguarded $event->payment->booking / $event->refund->payment->booking
  pattern fixed in the MarkBookingPaid/MarkBookingRefunded queued listeners.

289 tests passing.

app-modules/identity/tests/Feature/CustomerResourceTest.php

@@ -0,0 +1,35 @@
+<?php
+
+use App\Models\User;
+use Livewire\Livewire;
+use Modules\Identity\Database\Seeders\RolePermissionSeeder;
+use Modules\Identity\Filament\Resources\Customers\Pages\ListCustomers;
+
+beforeEach(function () {
+    $this->seed(RolePermissionSeeder::class);
+
+    $this->staff = User::factory()->create();
+    $this->staff->assignRole('support');
+});
+
+test('staff with view_customers can list customers', function () {
+    $this->actingAs($this->staff)->get('/admin/customers')->assertSuccessful();
+});
+
+test('the customer resource only lists users without any role', function () {
+    $customer = User::factory()->create();
+
+    $this->actingAs($this->staff);
+
+    Livewire::test(ListCustomers::class)
+        ->assertCanSeeTableRecords([$customer])
+        ->assertCanNotSeeTableRecords([$this->staff]);
+});
+
+test('a customer view page loads for staff', function () {
+    $customer = User::factory()->create();
+
+    $this->actingAs($this->staff)
+        ->get("/admin/customers/{$customer->id}")
+        ->assertSuccessful();
+});