Fix API7 Enterprise admin URL to use dashboard service

Changed adminUrl from dp-manager:7900 to dashboard:7080 for API7
Enterprise backend. The dp-manager service is for APISIX, while
API7EE requires the dashboard service which exposes the admin API.

This fixes the 404 errors when ADC tries to fetch configuration:
- GET /api/version
- GET /api/gateway_groups
- GET /api/schema/core

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

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

helm/api7ee-demo-k8s/values.yaml

@@ -217,8 +217,8 @@ api7:
 
   # API7 Gateway connection
   gateway:
-    # Use the actual DP Manager service for admin API
-    adminUrl: http://api7ee3-0-1759339083-dp-manager.api7ee.svc.cluster.local:7900
+    # Use the Dashboard service for API7 Enterprise admin API
+    adminUrl: http://api7ee3-0-1759339083-dashboard.api7ee.svc.cluster.local:7080
     adminKey: "" # Change this!
     group: default
     # Gateway service for traffic routing