[Studio] fix: connect system alerts page to APIs

[Loyal-Young]

Summary

• load system alerts through the existing opsService instead of page-level mock data;
• persist acknowledgement and clearing actions through /api/system-alerts;
• preserve the existing mock-mode workflow while adding loading and request-failure states;
• add an API contract test for the clear-acknowledged response payload.

Problem

The page imported systemAlerts from the mock module and changed only React state. In real API mode, alert data was never loaded from the server and acknowledgement/clear operations disappeared after a refresh, despite the backend and service layer already providing these endpoints.

Validation

• npm test -- ops.test.ts
• npm run lint (0 errors; 5 pre-existing warnings)
• npx tsc -b
• npx vite build