Initial monorepo scaffold

Turborepo + pnpm monorepo for k3s homelab cluster on Intel NUCs.

- Apps: Next.js web frontend, Express API (TypeScript, Dockerfiles, k8s manifests)
- Packages: shared UI, ESLint config, TypeScript config, Drizzle DB schemas
- Infra/Ansible: bare-metal provisioning with roles for common, k3s-server, k3s-agent, hardening
- Infra/Kubernetes: ArgoCD GitOps (app-of-apps + ApplicationSets), platform components
  (cert-manager, Traefik, CloudNativePG, Valkey, Longhorn, Sealed Secrets), namespaces
- Observability: kube-prometheus-stack, Loki, Promtail as ArgoCD Applications
- CI/CD: GitHub Actions for PR builds, preview deploys, production deploys
- DX: Taskfile, utility scripts, copier templates, Ubiquiti network docs

infra/kubernetes/platform/traefik/middleware-default-headers.yaml

@@ -0,0 +1,16 @@
+apiVersion: traefik.io/v1alpha1
+kind: Middleware
+metadata:
+  name: default-headers
+  namespace: platform
+spec:
+  headers:
+    browserXssFilter: true
+    contentTypeNosniff: true
+    frameDeny: true
+    stsIncludeSubdomains: true
+    stsPreload: true
+    stsSeconds: 31536000
+    customFrameOptionsValue: SAMEORIGIN
+    customRequestHeaders:
+      X-Forwarded-Proto: https