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

k8s/traefik/namespaces.yaml

@@ -0,0 +1,4 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: traefik

k8s/traefik/values.yaml

@@ -0,0 +1,31 @@
+deployment:
+  kind: DaemonSet
+
+ports:
+  web:
+    hostPort: 80
+  websecure:
+    hostPort: 443
+
+tolerations:
+  - key: "node-role.kubernetes.io/master"
+    operator: "Equal"
+    effect: "NoSchedule"
+  - key: "node-role.kubernetes.io/control-plane"
+    operator: "Equal"
+    effect: "NoSchedule"
+
+nodeSelector:
+  ingress-ready: "true"
+
+providers:
+  kubernetesIngress:
+    publishedService:
+      enabled: false
+
+service:
+  type: ClusterIP
+
+ingressClass:
+  enabled: true
+  isDefaultClass: true