Disable service discovery in chart default values

Service discovery requires Service Registry to be configured in
API7 Enterprise Dashboard first. Until the registry is configured,
ADC sync fails with: 'service registry not found'

Disabling service discovery to use static upstream nodes instead.

To re-enable:
1. Configure Service Registry in API7 Dashboard
2. Set api7.serviceDiscovery.enabled: true
3. Redeploy

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

helm/api7ee-demo-k8s/values.yaml

@@ -371,7 +371,7 @@ api7:
   # - RBAC permissions for services, endpoints (already configured in rbac-adc.yaml)
   # - Service must exist in Kubernetes
   serviceDiscovery:
-    enabled: true # Enable Kubernetes service discovery
+    enabled: false # Disabled: requires Service Registry configuration in API7 Dashboard
     namespace: "" # Leave empty to use release namespace
 
   # ============================================================================