fix(ipv6): use httpGet probes by default for IPv4 and IPv6 compatibility

Change default health probes from tcpSocket to httpGet to fix issue #68
where pods fail to start in IPv6-only clusters due to incompatible health checks.

Changes:
- Change default livenessProbe and readinessProbe to use httpGet with /health endpoint
- Add comprehensive IPv6 and dual-stack configuration documentation
- Document ipFamilyPolicy options (SingleStack, PreferDualStack, RequireDualStack)
- Document ipFamilies configuration for IPv4-only, IPv6-only, and dual-stack setups
- Add IPv6 Configuration section to README with examples
- Update Chart version from 2.5.0 to 2.5.1

The httpGet probe works with both IPv4 and IPv6 out of the box, while tcpSocket
may fail in IPv6-only environments. Jellyfin's /health endpoint is specifically
designed for health checks and verifies both HTTP and database connectivity.

Fixes: #68

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

charts/jellyfin/README.md.gotmpl

@@ -85,3 +85,32 @@ extraVolumeMounts:
   - name: hwa
     mountPath: /dev/dri
 ```
+
+## IPv6 Configuration
+
+This chart supports IPv6 and dual-stack networking configurations out of the box. Health probes use httpGet by default for compatibility with both IPv4 and IPv6.
+
+### IPv6-only Configuration
+
+For IPv6-only clusters:
+
+```yaml
+service:
+  ipFamilyPolicy: SingleStack
+  ipFamilies:
+    - IPv6
+```
+
+### Dual-stack Configuration
+
+For dual-stack clusters (both IPv4 and IPv6):
+
+```yaml
+service:
+  ipFamilyPolicy: PreferDualStack  # or RequireDualStack
+  ipFamilies:
+    - IPv4
+    - IPv6  # First family in the list is the primary
+```
+
+For more information about Kubernetes dual-stack networking, see: <https://kubernetes.io/docs/concepts/services-networking/dual-stack/>