Implements centralized tracking of SDR device allocation to prevent
multiple decoders from trying to use the same device simultaneously.
- Add sdr_device_registry with claim/release/status functions in app.py
- Update all SDR-based routes to claim devices on start and release on stop
- Return HTTP 409 with DEVICE_BUSY error when device is already in use
- Clear registry on /killall
- Skip device claims for remote connections (rtl_tcp, remote SBS)
Fixes#100Fixes#101
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>