Bump version to 0.8.0 and update persistence settings

This commit updates the Helm chart for Paperless AI from version
0.7.0 to 0.8.0, aligning it with the new app version 3.0.7. The
persistent storage configuration is modified by enabling the
storageClassName and changing its value to "default". Additionally,
the size of the persistent volume claim has been increased from 1Gi
to 2Gi to better accommodate data storage needs. These updates are
necessary to ensure compatibility with the latest application
requirements and to enhance the performance of persistent storage.
No breaking changes are introduced with this update.

charts/paperless-ai/Chart.yaml

@@ -1,7 +1,7 @@
 apiVersion: v2
 name: paperless-ai
 description: Ein Helm Chart für Paperless AI, basierend auf der Docker Compose Konfiguration.
-version: 0.7.0
+version: 0.8.0
 appVersion: 3.0.7
 keywords:
   - paperless-ai