fix(nrf24): support hold-back exit in active tools

[AndrewIsFat]

Proposed Changes

Add a shared NRF24 Back-button gesture for active tools. On three-button devices, holding Back for 700 ms draws the standard Bruce progress ring and exits after release. A short Back press remains available for selecting the previous Jammer mode.

Apply the gesture consistently to Spectrum, Jammer, MouseJack scanning, string injection, and DuckyScript execution. MouseJack cancellation now propagates through repeated commands and interruptible delays, and a cancelled scan returns directly to its menu instead of displaying "No devices found".

Types of Changes

Bugfix and user-interface consistency improvement.

Verification

Tested on a physical M5StickC Plus2:

• Spectrum ignored a short Back press and exited after a 910 ms held Back.
• MouseJack scan ignored a short Back press and exited after a 910 ms held Back.
• MouseJack returned directly to its menu after cancellation.
• Jammer retained short-Back previous-mode behavior and powered the radio down on exit.

Testing

• uv tool run platformio run -e m5stack-cplus2
• Serial navigation commands used to distinguish a short Back press from a 900 ms hold
• Physical radio detection and repeated tool entry on M5StickC Plus2

Linked Issues

No directly matching issue found.

User-Facing Change

Add hold-Back exit handling to active NRF24 Spectrum, Jammer, and MouseJack screens on three-button devices.

Further Comments

Non-three-button devices retain their existing Esc behavior.