ci: add Hugo blog CI/CD to k3s

- Enable Gitea Container Registry
- Dockerfile: nginx:alpine serving hugo public/
- Gitea Actions: build & push image + deploy to k3s
- k8s manifests: namespace hugo, deployment, service, ingress
- RBAC: allow runner to update deployments in hugo ns
- .gitignore: add public/ (CI builds it)

.gitignore

@@ -0,0 +1,17 @@
+# Hugo output - built by CI
+/public/
+
+# OS junk
+.DS_Store
+Thumbs.db
+*.swp
+*.swo
+
+# Editor
+.idea/
+.vscode/
+*.code-workspace
+
+# Hugo cache
+.hugo_build.lock
+resources/_gen/