Named voice rosters in the TTS catalog

/v1/models TTS entries now include a curated voices array and a voicesVerified date.

Each TTS entry in GET /v1/models now carries voices[] with { id, name, gender, styles }; roster order is meaningful, and the first entry is the provider default.

An empty voices array means the roster is not yet curated, not that the model has no voices.

TTS entries also carry voicesVerified, the curation date; it is null until a roster ships.

STT and LLM entries are unchanged.

No routing behavior changes; this is catalog metadata only.