fix(ingress): migrate from nginx to Traefik ingress controller

- Change ingressClassName from nginx to traefik
- Replace nginx configuration-snippet annotations with Traefik router annotations
- Extract security headers into dedicated Traefik Middleware CRD
- Update CI/CD pipeline to apply middleware manifest
- Document migration decision and deployment steps in README

ADR-002: Ingress Controller Migration (nginx → Traefik)
Migration strategy: in-place update

k8s/ingress.yaml

@@ -9,17 +9,11 @@ metadata:
     app.kubernetes.io/part-of: signalledger
   annotations:
     cert-manager.io/cluster-issuer: "letsencrypt-prod"
-    nginx.ingress.kubernetes.io/ssl-redirect: "true"
-    nginx.ingress.kubernetes.io/configuration-snippet: |
-      more_set_headers "Strict-Transport-Security: max-age=31536000; includeSubDomains; preload";
-      more_set_headers "X-Frame-Options: DENY";
-      more_set_headers "X-Content-Type-Options: nosniff";
-      more_set_headers "Referrer-Policy: strict-origin-when-cross-origin";
-      more_set_headers "Content-Security-Policy: default-src 'self'; script-src 'self' 'unsafe-inline' https://pagead2.googlesyndication.com https://partner.googleadservices.com https://tpc.googlesyndication.com; img-src 'self' data: https:; style-src 'self' 'unsafe-inline'; font-src 'self'; connect-src 'self'; frame-src https://googleads.g.doubleclick.net; object-src 'none'; base-uri 'self'; form-action 'self';";
-      more_set_headers "X-XSS-Protection: 1; mode=block";
-      more_set_headers "Permissions-Policy: accelerometer=(), camera=(), geolocation=(), gyroscope=(), magnetometer=(), microphone=(), payment=(), usb=()";
+    traefik.ingress.kubernetes.io/router.entrypoints: "websecure"
+    traefik.ingress.kubernetes.io/router.tls: "true"
+    traefik.ingress.kubernetes.io/router.middlewares: "openclaw-private-security-headers@kubernetescrd"
 spec:
-  ingressClassName: nginx
+  ingressClassName: traefik
   tls:
     - hosts:
         - signalledger.nl