Let users type or slide the check timeout

[nihey]

Summary

• Create and edit check dialogs now share a timeout control with both a seconds input and a slider.
• Values stay in sync, clamp to 1–60 seconds, and still submit as milliseconds.

Validation

• Added or updated tests for behavior changes
• Ran relevant tests and checks
• Updated relevant documentation
• Confirmed no production data, credentials, or populated .env files are included

Checklist

• Conventional commit subject used
• Scope is focused and ready for review

Test plan

• Open New check, choose HTTP or TCP, type a timeout in seconds and confirm the slider moves
• Drag the timeout slider and confirm the number field updates
• Edit an existing HTTP/TCP check and confirm both controls work the same way
• Values outside 1–60s clamp on blur