feat(helm): add login-flow auth mode to Helm chart (ADR-022)

Add Login Flow v2 as a fourth auth mode alongside basic, multi-user-basic,
and oauth. This enables multi-user deployments using Nextcloud's native
Login Flow v2 without requiring OAuth patches to user_oidc.

- Add loginFlow section to values.yaml with token encryption config
- Add login-flow env vars, args, volume mounts to deployment.yaml
- Add login-flow secret and oauth-storage PVC templates
- Add loginFlowSecretName helper, update dataStorageEnabled
- Add multi-user-basic and login-flow sections to NOTES.txt
- Add version footer and ArtifactHub changelog annotations
- Update README with 4 auth modes and docker-compose profiles

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

charts/nextcloud-mcp-server/Chart.yaml

@@ -25,6 +25,15 @@ annotations:
   # Grafana dashboard support
   grafana_dashboard: "true"
   grafana_dashboard_folder: "Nextcloud MCP"
+  artifacthub.io/changes: |
+    - kind: added
+      description: Login Flow v2 auth mode for Helm chart (ADR-022)
+    - kind: added
+      description: Multi-user BasicAuth guidance in post-install NOTES
+    - kind: added
+      description: Version and changelog info in post-install NOTES
+    - kind: changed
+      description: Updated appVersion to 0.64.4
 dependencies:
   - name: qdrant
     version: "1.17.0"