Add TypeScript SDK and playlists UI
Add a full TypeScript SDK under sdk/typescript (client, transports,
APIs, types, errors, plugin registry), with package/bun config,
lockfile, README, CLAUDE and tests. Add web UI playlist pages and
components (Playlists, PlaylistDetails, modals, styles), GraphQL
queries/mutations and generated hooks. Fix GraphQL schema imports to
include track types for saved and smart playlists.