fix: skip keycloak hook when profile inactive and update stale PRM test

Add DNS pre-check (getent hosts keycloak) to the post-installation hook
so it exits instantly when the keycloak profile is not active, instead of
retrying for ~2.5 minutes. Also update test_prm_endpoint to assert the
AS proxy URL (localhost:8001) per ADR-023, replacing the stale Nextcloud
URL (localhost:8080).

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

tests/server/oauth/test_scope_authorization.py

@@ -33,7 +33,7 @@ async def test_prm_endpoint():
         assert prm_data["resource"] == "http://localhost:8001/mcp"
         assert "notes:read" in prm_data["scopes_supported"]
         assert "notes:write" in prm_data["scopes_supported"]
-        assert "http://localhost:8080" in prm_data["authorization_servers"]
+        assert "http://localhost:8001" in prm_data["authorization_servers"]
         assert "header" in prm_data["bearer_methods_supported"]
         assert "RS256" in prm_data["resource_signing_alg_values_supported"]