feat(persistence): add cache volume persistence support

Add dedicated cache volume configuration to reduce wear on SD cards and improve
performance by allowing cache to be stored on separate storage.

Changes:
- Add persistence.cache configuration in values.yaml with support for:
  - PVC (default type when enabled)
  - hostPath for direct host mount
  - emptyDir (default when disabled)
- Add cache volume mount at /cache in deployment
- Add cache PersistentVolumeClaim template
- Support for existing PVC via existingClaim
- Configurable size (default 10Gi), accessMode, storageClass, and annotations
- Update Chart version from 2.5.0 to 2.5.1
- Add Artifact Hub changelog annotation

The cache volume is disabled by default to maintain backward compatibility.
Users can enable it via:

```yaml
persistence:
  cache:
    enabled: true
    type: pvc
    size: 10Gi
```

This addresses the use case mentioned in #62 where users want to avoid SD card
wear by storing cache on separate persistent storage.

Fixes: #62

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Aleksei Sviridkin <f@lex.la>

charts/jellyfin/Chart.yaml

@@ -8,5 +8,9 @@ keywords:
   - jellyfin
   - media
   - self-hosted
-version: 2.5.0
+version: 2.5.1
 appVersion: 10.11.2
+annotations:
+  artifacthub.io/changes: |
+    - kind: added
+      description: Add persistence.cache configuration for dedicated cache volume support