fix: restore lazy PyPIMixin import to prevent circular import crash (#1232)

The top-level import of PyPIMixin introduced in #1231 causes a circular
import at startup: DRF settings → DomainBasedPermission → pulp_python
views → rest_framework.viewsets → (circular). This crashes all API pods
with CrashLoopBackOff.

Restore the lazy import inside has_permission() where it was originally.

Assisted-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: decko

pulp_service/pulp_service/app/authorization.py

@@ -11,8 +11,6 @@
 from pulpcore.plugin.models import Domain
 from pulpcore.plugin.util import extract_pk, get_domain_pk
 
-from pulp_python.app.pypi.views import PyPIMixin
-
 from pulp_service.app.models import DomainOrg
 
 _logger = logging.getLogger(__name__)
@@ -52,6 +50,8 @@ def has_permission(self, request, view):
 
         # Allow safe requests on PyPI views and public domains for all users
         if request.method in SAFE_METHODS:
+            from pulp_python.app.pypi.views import PyPIMixin
+
             if isinstance(view, PyPIMixin):
                 return True
             domain = getattr(request, "pulp_domain", None)