Banshee Enhancement: Add RTL-SDR (RTL2832U) support via USB host for RF scanning + audio demod #278
Description
Please add support for using an RTL-SDR (RTL2832U-based USB SDR dongle) with the Banshee so GhostESP can do real-time RF scanning and optionally demod/play back audio from selected signals (e.g., FM/NFM/AM) through the Banshee’s audio path / UI.
RTL-SDR is a widely used low-cost SDR platform that exposes raw I/Q samples over USB and enables wideband scanning + demodulation in software. 
Banshee already feels like a perfect “field UI + power + hub + control” companion device for SDR workflows (Wi-Fi/BLE/NFC/GPS/SD/USB features already make it a strong portable platform). 
Why this matters / use cases
• Portable spectrum reconnaissance alongside existing GhostESP capabilities
• Quick frequency search + “tap to demod” (FM/NFM/AM) for situational awareness
• Use Banshee as a single handheld interface instead of needing a laptop/phone
Requested features (MVP → future)
MVP
• Detect an attached RTL-SDR
• Tune frequency + set mode (FM/NFM/AM) + basic gain
• Basic spectrum/waterfall view
• Record IQ or audio to SD with timestamp (+ optionally GPS)
Nice-to-have
• Frequency “scan list” with dwell time + squelch thresholds
• Autostart scanning profiles
• Export logs in a simple CSV format
So the implementation may require one of these approaches:
Proposed implementation approaches
• RTL-SDR plugs into high-speed USB
• Host runs rtl_tcp/decoder/demod + sends:
• waterfall and configuration to Banshee Screen
• audio stream (compressed) to Banshee for playback
• Banshee acts as UI/controller + logger (and could still do GPS-tagging)