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/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