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/values.yaml

@@ -85,8 +85,17 @@ service:
   # -- Service type (ClusterIP, NodePort, or LoadBalancer).
   type: ClusterIP
   # -- Configure dual-stack IP family policy. See: https://kubernetes.io/docs/concepts/services-networking/dual-stack/
+  # Options: SingleStack, PreferDualStack, RequireDualStack
+  # For IPv6-only clusters, use "SingleStack" with ipFamilies: ["IPv6"]
+  # For dual-stack, use "PreferDualStack" or "RequireDualStack" with ipFamilies: ["IPv4", "IPv6"] or ["IPv6", "IPv4"]
   ipFamilyPolicy: ""
   # -- Supported IP families (IPv4, IPv6).
+  # Examples:
+  #   IPv4 only: ["IPv4"]
+  #   IPv6 only: ["IPv6"]
+  #   Dual-stack (IPv4 primary): ["IPv4", "IPv6"]
+  #   Dual-stack (IPv6 primary): ["IPv6", "IPv4"]
+  # Note: When using IPv6, ensure your health checks are compatible (consider using httpGet instead of tcpSocket)
   ipFamilies: []
   # -- Specific IP address for the LoadBalancer.
   loadBalancerIP: ""
@@ -134,20 +143,24 @@ resources: {}
   #   memory: 128Mi
 
 # -- Configure liveness probe for Jellyfin.
+# Uses httpGet for compatibility with both IPv4 and IPv6.
 livenessProbe:
-  initialDelaySeconds: 10
-  tcpSocket:
+  httpGet:
+    path: /health
     port: http
+  initialDelaySeconds: 10
   # successThreshold: 1
   # failureThreshold: 3
   # timeoutSeconds: 1
   # periodSeconds: 10
 
 # -- Configure readiness probe for Jellyfin.
+# Uses httpGet for compatibility with both IPv4 and IPv6.
 readinessProbe:
-  initialDelaySeconds: 10
-  tcpSocket:
+  httpGet:
+    path: /health
     port: http
+  initialDelaySeconds: 10
   # successThreshold: 1
   # failureThreshold: 3
   # timeoutSeconds: 1