feat: add manual monitor check action

[jhcpeixoto]

Summary

• add an admin endpoint to run a monitor check immediately without waiting for the next scheduled interval
• reuse the existing heartbeat job path so manual checks update status, checks, incidents, notifications, and maintenance handling consistently
• add a Check now action to uptime, infrastructure, and PageSpeed monitor action menus

Refs #2389, specifically the wishlist request for an easy way to check a site immediately.

Verification

• npm run test:unit:services -- --runTestsByPath test/unit/services/monitorService.test.ts test/unit/services/superSimpleQueue.test.ts
• npm run build:openapi
• npm run build (server)
• npm run build (client)
• npm run format-check (server)
• npm run format-check (client)
• targeted ESLint on changed server/client source files
• git diff --check