feat: add superadmin health center

frontend/superadmin/src/service/HealthService.js

@@ -0,0 +1,21 @@
+import { requestJson } from './apiClient';
+
+export const HealthService = {
+    async getOverview({ tenant_id, start_at, end_at, upload_stuck_hours } = {}) {
+        const iso = (d) => {
+            if (!d) return undefined;
+            const date = d instanceof Date ? d : new Date(d);
+            if (Number.isNaN(date.getTime())) return undefined;
+            return date.toISOString();
+        };
+
+        const query = {
+            tenant_id,
+            start_at: iso(start_at),
+            end_at: iso(end_at),
+            upload_stuck_hours
+        };
+
+        return requestJson('/super/v1/health/overview', { query });
+    }
+};