Feature: Sub-GHz StreetPass (Signal Link)

[evanmiller2112]

Sub-GHz StreetPass ("Signal Link")

Passively discover other FlippyMon players via Sub-GHz beacon broadcasting.

Tasks

• Design beacon packet format (~32 bytes: trainer ID, name, lead monster, badges)
• Implement periodic beacon broadcasting (every ~30 seconds)
• Add beacon listener for other FlippyMon players
• Create SD card storage for encountered trainers (up to ~50)
• Build "Signal Log" menu to view encounters
• Add ghost trainer battles from encounters
• "Trainers Met" counter and achievements