cathar v0.3.0

Added

• Main-path resampling. A shared Kaiser-windowed sinc resampler (16 lobes,
  β = 9, arbitrary ratio) with cutoff tracking the lower Nyquist, so
  downsampling is anti-aliased and upsampling adds no imaging. Exposed as the
  resample free function, AudioData::resample(target_rate), and a new
  resample CLI command. Any stage can now bring mixed-rate inputs to a common
  rate.

Changed

• bandwidth_extend (enhance) now uses the shared resampler instead of its
  own inline windowed-sinc loop.