fix: remove serviceName from StatefulSets (not needed)

Removed serviceName field from both StatefulSets since stable pod DNS
is not required for single-replica IRC applications. StatefulSets only
need serviceName when using headless Services for stable network identities.

Also removed statefulset-has-servicename ignore since it's now properly fixed.

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

.gitea/workflows/best-practices.yaml

@@ -40,7 +40,6 @@ jobs:
               --ignore-test container-security-context-readonlyrootfilesystem \
               --ignore-test container-image-tag \
               --ignore-test container-security-context-user-group-id \
-              --ignore-test statefulset-has-servicename \
               --ignore-test probe-not-identical \
               --output-format ci
           fi