Add Gitea Actions runner for automated CI/CD pipeline

- Runner deployment with host mode execution and kubectl access
- RBAC for creating Kaniko build pods
- Workflow triggers on push to main: Kaniko build → registry push → gitops update → ArgoCD sync

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infrastructure/gitea-runner/runner-secret.yaml

@@ -0,0 +1,8 @@
+apiVersion: v1
+kind: Secret
+metadata:
+  name: runner-secret
+  namespace: build
+type: Opaque
+stringData:
+  token: "LfMBBZOvAHsP4YTBHyl8gwVPYKTxQLLXsMB7YlCy"