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/identity-ingress.yaml

@@ -0,0 +1,23 @@
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: notesnook-auth
+  namespace: notesnook
+  annotations:
+    cert-manager.io/cluster-issuer: letsencrypt-prod
+    traefik.ingress.kubernetes.io/router.entrypoints: websecure
+spec:
+  ingressClassName: traefik
+  rules:
+    - host: auth.notes.aleshym.co
+      http:
+        paths:
+          - path: /
+            pathType: Prefix
+            backend:
+              service:
+                name: notesnook-identity
+                port: { name: http }
+  tls:
+    - hosts: ["auth.notes.aleshym.co"]
+      secretName: notesnook-auth-tls