fix: fetch actual agent/environment counts from server for tenant dashboard

The dashboard was showing hardcoded zeroes for agent and environment usage.
Now fetches real counts via M2M API from the tenant's server.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/tenant/TenantDashboardPage.tsx

@@ -54,9 +54,8 @@ export function TenantDashboardPage() {
 
   const agentLimit = data.limits?.['agents'] ?? -1;
   const envLimit = data.limits?.['environments'] ?? -1;
-  // Dashboard doesn't expose usage counts directly — show limit info from license
-  const agentUsed = 0;
-  const envUsed = 0;
+  const agentUsed = data.agentCount ?? 0;
+  const envUsed = data.environmentCount ?? 0;
 
   return (
     <div style={{ padding: 24, display: 'flex', flexDirection: 'column', gap: 20 }}>