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/traefik/kustomization.yaml

@@ -0,0 +1,12 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+- namespaces.yaml
+helmCharts:
+- name: traefik
+  namespace: traefik
+  includeCRDs: true
+  releaseName: traefik
+  repo: https://traefik.github.io/charts
+  version: 39.0.7
+  valuesFile: values.yaml