Support an optional remote pit display and control link

[PurpleSentinel]

Parent: #23

Summary

Define a safe companion link for pit crew to view timer state or prepare settings using future wireless or wired-capable hardware.

Acceptance criteria

• Keep the driver display authoritative and fully functional offline.
• Separate read-only status from explicitly permitted control actions.
• Require pairing or physical authorization for remote changes.
• Handle disconnects without altering session timing.
• Prototype the protocol independently of any single radio technology.

Roadmap group

Sensors, power, and hardware expansion