refactor: migrate from ingress-nginx to Traefik v3 (#254)

## Summary

- Replace ingress-nginx 4.15.1 with Traefik v3 (Helm chart 39.0.7) as ingress controller
- Convert nginx-specific annotations to Traefik Middleware CRDs
- Update setup script selectors, namespaces, and readiness checks
- Add `.claude/settings.local.json` to `.gitignore`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #254

k8s/nginx/kustomization.yaml

@@ -1,12 +0,0 @@
-apiVersion: kustomize.config.k8s.io/v1beta1
-kind: Kustomization
-resources:
-- namespaces.yaml
-helmCharts:
-- name: ingress-nginx
-  namespace: ingress-nginx
-  includeCRDs: true
-  releaseName: ingress-nginx
-  repo: https://kubernetes.github.io/ingress-nginx
-  version: 4.15.1
-  valuesFile: https://raw.githubusercontent.com/kubernetes/ingress-nginx/main/hack/manifest-templates/provider/kind/values.yaml