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

k8s/erpnext/oauth2-proxy.yaml

@@ -0,0 +1,82 @@
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: oauth2-proxy-secrets
+  namespace: erpnext
+type: Opaque
+stringData:
+  OAUTH2_PROXY_CLIENT_ID: "371747520893682044"
+  OAUTH2_PROXY_CLIENT_SECRET: "Wka1L8RYFYeKHrzMOadDfQRXWlCnM6x2JKL2QBTmV3WHdaYY2OiodVZgK0MYdiFl"
+  OAUTH2_PROXY_COOKIE_SECRET: "st_biHMwZOrFbrigSmnEdRG5ZCoULrktjAvPGcUrqw0"
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: oauth2-proxy
+  namespace: erpnext
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: oauth2-proxy
+  template:
+    metadata:
+      labels:
+        app: oauth2-proxy
+    spec:
+      containers:
+        - name: oauth2-proxy
+          image: quay.io/oauth2-proxy/oauth2-proxy:v7.7.1
+          args:
+            - --provider=oidc
+            - --oidc-issuer-url=https://auth.expertfab.de
+            - --upstream=http://erpnext:8080
+            - --http-address=0.0.0.0:4180
+            - --email-domain=*
+            - --scope=openid profile email
+            - --skip-provider-button=true
+            - --cookie-secure=true
+            - --cookie-samesite=lax
+            - --cookie-domain=expertfab.de
+            - --whitelist-domain=expertfab.de
+            - --whitelist-domain=www.expertfab.de
+            - --reverse-proxy=true
+            - --set-xauthrequest=true
+          env:
+            - name: OAUTH2_PROXY_CLIENT_ID
+              valueFrom:
+                secretKeyRef:
+                  name: oauth2-proxy-secrets
+                  key: OAUTH2_PROXY_CLIENT_ID
+            - name: OAUTH2_PROXY_CLIENT_SECRET
+              valueFrom:
+                secretKeyRef:
+                  name: oauth2-proxy-secrets
+                  key: OAUTH2_PROXY_CLIENT_SECRET
+            - name: OAUTH2_PROXY_COOKIE_SECRET
+              valueFrom:
+                secretKeyRef:
+                  name: oauth2-proxy-secrets
+                  key: OAUTH2_PROXY_COOKIE_SECRET
+          ports:
+            - containerPort: 4180
+          resources:
+            requests:
+              cpu: 50m
+              memory: 64Mi
+            limits:
+              cpu: 100m
+              memory: 128Mi
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: oauth2-proxy
+  namespace: erpnext
+spec:
+  selector:
+    app: oauth2-proxy
+  ports:
+    - port: 4180
+      targetPort: 4180