v0.4.0

Storage & URL Migration

• Migrated cloud storage bucket from sign-lanugage-datasets.sign-mt.cloud to datasets.sigma-sign-language.com
• Updated AUTSL dataset label paths (public/autsl_*.csv → public/autsl/autsl_*.csv)
• Updated NGT Corpus index path (public/ngt.json → public/ngt-corpus/ngt.json)
• Updated Phoenix2014-T annotations path (public/phoenix-annotations.tar.gz → public/phoenix/phoenix-annotations.tar.gz)
• Updated NGT Corpus alternative mirror URL