Sprint 5: PartnerCustomerListView — partner-scoped customer list

- admin_api/views.py: PartnerCustomerListView — distinct users who've
  booked partner's events, annotated with bookings_count + total_spent
  aggregates, search by email/name, paginated [1,200]
- admin_api/urls.py: wire partners/me/customers/

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin_api/urls.py

@@ -35,6 +35,8 @@ urlpatterns = [
     path('partners/me/events/<int:event_pk>/tiers/<int:tier_pk>/', views.PartnerMeEventTierDetailView.as_view(), name='partner-me-event-tier-detail'),
     # Partner-Me: bookings (Sprint 4)
     path('partners/me/bookings/', views.PartnerBookingListView.as_view(), name='partner-me-bookings'),
+    # Partner-Me: customers (Sprint 5)
+    path('partners/me/customers/', views.PartnerCustomerListView.as_view(), name='partner-me-customers'),
     path('users/metrics/', views.UserMetricsView.as_view(), name='user-metrics'),
     path('users/', views.UserListView.as_view(), name='user-list'),
     path('users/<int:pk>/', views.UserDetailView.as_view(), name='user-detail'),