BLE Beacon + Firmware Improvements

[7086cmd]

Upgrade BLE beacon firmware for reliability, security, and better onboarding.

Tasks to include:

• Address BLE scanning and provisioning (BluFi) TODOs
• OTA update handler completion
• Key storage and crypto improvements
• Enhance error handling for embedded
• Add tests for time-windowed nonce validation and replay protection

See critical todos and refactoring plan