Add SoftwareFPGA class that imports golden_reference functions to
replicate the FPGA pipeline in software, enabling bit-accurate replay
of raw IQ, FPGA co-sim, and HDF5 recordings through the same
dashboard path as live data.
New modules: software_fpga.py, replay.py (ReplayEngine + 3 loaders)
Enhanced: WaveformConfig model, extract_targets_from_frame() in
processing, ReplayWorker with thread-safe playback controls,
dashboard replay UI with transport controls and dual-dispatch
FPGA parameter routing.
Removed: ReplayConnection (from radar_protocol, hardware, dashboard,
tests) — replaced by the unified replay architecture.
150/150 tests pass, ruff clean.
Jason