Add a 'Disarm for 15 minutes' menu option

[kasparovabi]

When a coworker will be at your desk for a few minutes, fully disarming and remembering to re-arm is easy to forget. A temporary disarm would help.

What to do

• Add a menu item in Sources/BustedApp/MenuBarController.swift, next to Arm / Disarm, e.g. "Disarm for 15 minutes".
• When chosen, disarm now and schedule a re-arm after the interval (a Timer or Task sleep on the main actor).
• Manually arming or disarming should cancel the pending re-arm.

Acceptance criteria

• Choosing the option disarms immediately and re-arms automatically after the interval.
• Manually toggling arm/disarm cancels the scheduled re-arm.
• The menu bar reflects the current state (the existing refreshTitle() already handles this).

Pointers

• Arm and disarm go through wiring.arm(source:) and wiring.disarm(source:) in Sources/BustedApp/AppWiring.swift.
• Keep the interval a constant for now; making it configurable can be a follow-up.