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/db-statefulset.yaml

@@ -0,0 +1,42 @@
+apiVersion: apps/v1
+kind: StatefulSet
+metadata:
+  name: notesnook-db
+  namespace: notesnook
+spec:
+  serviceName: notesnook-db
+  replicas: 1
+  selector:
+    matchLabels:
+      app: notesnook-db
+  template:
+    metadata:
+      labels:
+        app: notesnook-db
+    spec:
+      containers:
+        - name: mongod
+          image: mongo:7.0.12
+          args: ["--replSet", "rs0", "--bind_ip_all"]
+          ports:
+            - containerPort: 27017
+              name: mongo
+          volumeMounts:
+            - name: dbdata
+              mountPath: /data/db
+          readinessProbe:
+            exec:
+              command: ["mongosh", "--quiet", "--eval", "db.runCommand('ping').ok"]
+            initialDelaySeconds: 10
+            periodSeconds: 15
+          resources:
+            requests: { cpu: "100m", memory: "256Mi" }
+            limits: { cpu: "1000m", memory: "1Gi" }
+  volumeClaimTemplates:
+    - metadata:
+        name: dbdata
+      spec:
+        accessModes: ["ReadWriteOnce"]
+        resources:
+          requests:
+            storage: 10Gi