v0.14.0

v0.14.0 — split, pan, eq, key-match, sidechain-duck

Five new audio editing primitives, zero new dependencies:

- /v1/audio/split: equal-time (N parts) or silence-based split; ZIP output
- /v1/audio/pan: stereo pan via ffmpeg pan filter; position [-1.0, 1.0]
- /v1/audio/eq: parametric EQ via ffmpeg equalizer chain; any number of bands
- /v1/audio/key-match: detect source key (chord-detect) + pitch-shift to
  target key (stretch); _parse_key_root handles sharps/flats/modes
- /v1/audio/sidechain-duck: ffmpeg sidechaincompress; primary duck on trigger;
  threshold_db/ratio/attack_ms/release_ms

MCP: 58 tools total.
README: all new endpoints and tools documented.