feat: add catalogue image management (#1)

- Add CatalogueImage model with FK to Product
- Add image resize service (strict/non-strict modes with configurable dimensions)
- Add CRUD API endpoints with admin-only write permissions
- Add catalogue_images field to product listing/detail endpoints
- Serve media files in development via static()
- 28 TDD tests covering model, API, permissions, resize, and product listing

tienda_ilusion/config/urls.py

@@ -14,6 +14,8 @@ Including another URLconf
     1. Import the include() function: from django.urls import include, path
     2. Add a URL to urlpatterns:  path('blog/', include('blog.urls'))
 """
+from django.conf import settings
+from django.conf.urls.static import static
 from django.contrib import admin
 from django.urls import include, path
 from rest_framework_simplejwt.views import (
@@ -32,3 +34,6 @@ urlpatterns = [
          name='token_refresh'),
     path('api/users/', include('users.urls')),
 ]
+
+if settings.DEBUG:
+    urlpatterns += static(settings.MEDIA_URL, document_root=settings.MEDIA_ROOT)