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/argocd/appsets/previews.yaml

@@ -0,0 +1,34 @@
+apiVersion: argoproj.io/v1alpha1
+kind: ApplicationSet
+metadata:
+  name: apps-preview
+  namespace: argocd
+spec:
+  goTemplate: true
+  goTemplateOptions: ["missingkey=error"]
+  generators:
+    - pullRequest:
+        github:
+          owner: OWNER
+          repo: homelab
+        requeueAfterSeconds: 60
+  template:
+    metadata:
+      name: "preview-{{ .number }}"
+    spec:
+      project: default
+      source:
+        repoURL: https://github.com/OWNER/homelab.git
+        targetRevision: "{{ .branch }}"
+        path: apps/*/k8s/overlays/preview
+        kustomize:
+          nameSuffix: "-pr{{ .number }}"
+      destination:
+        server: https://kubernetes.default.svc
+        namespace: "preview-{{ .number }}"
+      syncPolicy:
+        automated:
+          prune: true
+          selfHeal: true
+        syncOptions:
+          - CreateNamespace=true