feat(kong): add system-account-reports route to reporting-service

Add Kong route for the new system account reports API endpoint
at /api/v1/system-account-reports, forwarding to reporting-service.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/api-gateway/kong.yml

@@ -177,6 +177,11 @@ services:
         paths:
           - /api/v1/export
         strip_path: false
+      # [2026-01-04] 新增：系统账户报表路由
+      - name: reporting-system-accounts
+        paths:
+          - /api/v1/system-account-reports
+        strip_path: false
 
   # ---------------------------------------------------------------------------
   # Authorization Service - 授权服务