Update API spec: add preset reference audio documentation

Add HF Dataset reference audio support

Add MPLCONFIGDIR and NUMBA_CACHE_DIR env vars

Fix checkpoint directory permissions and unify env vars

Fix cache directory permissions with absolute path

Add seed-vc Python files without binary examples

Fix module import path for seed-vc

Remove source_original.wav from Dockerfile

Remove default reference audio, use uploaded ref instead

Add Git LFS config

initial commit