Migrate Joplin to K3s and add existing k8s manifests

- New k8s/joplin/ deployment for note.expertfab.de (Postgres + Server +
  Traefik ingress with cert-manager), replicas=2 to match cluster size
- coredns-custom.yaml: route note.expertfab.de internally to Traefik LB
- Commit previously-built k8s manifests (documenso, erpnext oauth2-proxy,
  paperless oauth2-proxy) that were running but not in git
- docs/access.md: add Joplin section and Documenso/Cloudflare entries

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

k8s/joplin/postgres.yaml

@@ -0,0 +1,96 @@
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: joplin-postgres
+  namespace: joplin
+type: Opaque
+stringData:
+  POSTGRES_DB: joplin
+  POSTGRES_USER: joplin
+  POSTGRES_PASSWORD: "TXIlCX4DUdKZuqbYt2lTaxMXvz6cJi"
+---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: joplin-postgres-data
+  namespace: joplin
+spec:
+  accessModes: ["ReadWriteOnce"]
+  storageClassName: longhorn-joplin
+  resources:
+    requests:
+      storage: 10Gi
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: joplin-postgres
+  namespace: joplin
+spec:
+  replicas: 1
+  strategy:
+    type: Recreate
+  selector:
+    matchLabels:
+      app: joplin-postgres
+  template:
+    metadata:
+      labels:
+        app: joplin-postgres
+    spec:
+      containers:
+        - name: postgres
+          image: postgres:16-alpine
+          ports:
+            - containerPort: 5432
+          envFrom:
+            - secretRef:
+                name: joplin-postgres
+          env:
+            - name: PGDATA
+              value: /var/lib/postgresql/data/pgdata
+          volumeMounts:
+            - name: data
+              mountPath: /var/lib/postgresql/data
+          startupProbe:
+            exec:
+              command: ["pg_isready", "-U", "joplin", "-d", "joplin"]
+            initialDelaySeconds: 10
+            periodSeconds: 10
+            timeoutSeconds: 5
+            failureThreshold: 30
+          readinessProbe:
+            exec:
+              command: ["pg_isready", "-U", "joplin", "-d", "joplin"]
+            periodSeconds: 10
+            timeoutSeconds: 5
+          livenessProbe:
+            exec:
+              command: ["pg_isready", "-U", "joplin", "-d", "joplin"]
+            periodSeconds: 30
+            timeoutSeconds: 5
+            failureThreshold: 5
+          resources:
+            requests:
+              cpu: 100m
+              memory: 256Mi
+            limits:
+              cpu: 1000m
+              memory: 1Gi
+      volumes:
+        - name: data
+          persistentVolumeClaim:
+            claimName: joplin-postgres-data
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: joplin-postgres
+  namespace: joplin
+spec:
+  selector:
+    app: joplin-postgres
+  ports:
+    - port: 5432
+      targetPort: 5432