Three more torch-free, cached building blocks → 11 engines total.

- POST /loudness → BS.1770 integrated LUFS (pyloudnorm) + sample/true-peak (4×
  oversample) + crest + the gain to hit each delivery target (-14 streaming, -9
  club, reference_postprod_master). The mastering numbers PLN + hexa gate on.
  engines/loudness.py; pyloudnorm added to requirements-deploy (pure-python, tiny).
- POST /spectrum → FFT-AS-A-SERVICE (PLN's ask): a downsampled, render-ready
  spectrogram bands×frames, 0..1 normalized; mel (perceptual, for visuals) or
  log-linear; frames=1 collapses to a single averaged FFT spectrum. Bounded
  payload so it caches cheaply. signal.spectrum().
- POST /naming → convention-compliant sample name (NN_role_character) from the
  MEASURED role + character, never the file name. naming.py vendored from the
  Foundry (drift-guarded); character_of() derives the adjective from features.

Validated in the torch-free container (LUFS -19.1 w/ gain +5.1/+10.1; mel band
centers; "07_melodic_warm" lint-clean). 58/58 tests (test_extra.py: engines +
endpoints + naming drift guard + character_of). Image now serves emotion/features/
samples/grade/onsets/waveform/analyze/loudness/spectrum/naming + separate-503.