Introduce an optional Burst LUT optimization for Laurent-based burst modulation, enabled via --with-burst-lut.
- Add precomputed Laurent LUT tables (float and int16 I/Q variants) - Generate LUT at initialization (prepareBurstLUT) - Use LUT-based modulation for sps=4 when enabled - Keep original modulateBurstLaurent() as fallback - Add configure.ac option and USE_BURST_LUT define
This reduces runtime computation by replacing per-burst Laurent processing with memcpy-based LUT lookups.
