feat(notesnook): migrate self-hosted Notesnook to k3s

Adds apps/notesnook (namespace, config, mongo rs0 StatefulSet, minio,
identity/sync/sse/monograph deployments + Traefik/cert-manager ingresses)
and argocd/notesnook.yaml. Secret applied out-of-band (only .example committed).
Includes design spec + implementation plan under docs/superpowers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/notesnook/kustomization.yaml

@@ -0,0 +1,26 @@
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: notesnook
+resources:
+  - namespace.yaml
+  - notesnook-config.yaml
+  - db-service.yaml
+  - db-statefulset.yaml
+  - db-init-job.yaml
+  - minio-pvc.yaml
+  - minio-deployment.yaml
+  - minio-service.yaml
+  - minio-bucket-job.yaml
+  - identity-deployment.yaml
+  - identity-service.yaml
+  - identity-ingress.yaml
+  - sync-deployment.yaml
+  - sync-service.yaml
+  - sync-ingress.yaml
+  - sse-deployment.yaml
+  - sse-service.yaml
+  - sse-ingress.yaml
+  - monograph-deployment.yaml
+  - monograph-service.yaml
+  - monograph-ingress.yaml
+  - attachments-ingress.yaml