NiceVois Seed-VC integration source

Seed-VC upstream revision: 51383efd921027683c89e5348211d93ff12ac2a8
Official source: https://github.com/Plachtaa/seed-vc
License: upstream GPL-3.0 text is in upstream/LICENSE.
NiceVois Seed integration changes in nicevois-seed/ are supplied under those
GPL-3.0 terms. Existing third-party notices and licenses remain applicable.
PlayVoice finishing code: https://github.com/PlayVoice/BigVGAN (MIT code).
That code license is not a grant for its separately released model weights.

This archive includes the matching engine code, training/render/export changes,
separator helper code, configuration, and checksum manifest. It excludes voice
recordings, customer checkpoints, secrets, all model weights, and audio examples.
Use the official installation instructions and the voice ZIP's README. The
NiceVois finishing weight is NOT redistributed in a voice or source package.
The local upstream Seed interface can sound different from hosted NiceVois.

The service source documents the isolated cloud recipe; it is not required to
run app_svc.py locally. Its build-time filesystem paths must be configured for
your own machine. Seed asset acquisition uses the official Seed-VC model page,
https://huggingface.co/Plachta/Seed-VC . Runtime code validates all asset hashes.
