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/erpnext/ingress-auth.yaml

@@ -0,0 +1,80 @@
+---
+# /app/* — Zitadel Auth via oauth2-proxy (beide Domains)
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: erpnext-app-auth
+  namespace: erpnext
+  annotations:
+    cert-manager.io/cluster-issuer: letsencrypt
+    traefik.ingress.kubernetes.io/router.entrypoints: websecure
+    traefik.ingress.kubernetes.io/router.tls: "true"
+    traefik.ingress.kubernetes.io/router.priority: "100"
+spec:
+  ingressClassName: traefik
+  rules:
+    - host: expertfab.de
+      http:
+        paths:
+          - path: /app
+            pathType: Prefix
+            backend:
+              service:
+                name: oauth2-proxy
+                port:
+                  number: 4180
+    - host: www.expertfab.de
+      http:
+        paths:
+          - path: /app
+            pathType: Prefix
+            backend:
+              service:
+                name: oauth2-proxy
+                port:
+                  number: 4180
+  tls:
+    - hosts:
+        - expertfab.de
+        - www.expertfab.de
+      secretName: expertfab-tls
+---
+# /oauth2/* — OIDC Callback-Handling (beide Domains)
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: erpnext-oauth2
+  namespace: erpnext
+  annotations:
+    cert-manager.io/cluster-issuer: letsencrypt
+    traefik.ingress.kubernetes.io/router.entrypoints: websecure
+    traefik.ingress.kubernetes.io/router.tls: "true"
+    traefik.ingress.kubernetes.io/router.priority: "100"
+spec:
+  ingressClassName: traefik
+  rules:
+    - host: expertfab.de
+      http:
+        paths:
+          - path: /oauth2
+            pathType: Prefix
+            backend:
+              service:
+                name: oauth2-proxy
+                port:
+                  number: 4180
+    - host: www.expertfab.de
+      http:
+        paths:
+          - path: /oauth2
+            pathType: Prefix
+            backend:
+              service:
+                name: oauth2-proxy
+                port:
+                  number: 4180
+  tls:
+    - hosts:
+        - expertfab.de
+        - www.expertfab.de
+      secretName: expertfab-tls