v2.5.0 — OpenAI gpt-4o-transcribe + gpt-4o-mini-transcribe aliases

Exposes OpenAI's March-2025 GPT-4o-based transcription models as
first-class LiteLLM aliases alongside the existing openai-whisper
(whisper-1). Lower WER than whisper, streaming partial chunks, same
/v1/audio/transcriptions endpoint.

Not yet wired into fallbacks.json. Output format caveat: the new
models only support json / text, not srt / vtt / verbose_json — keep
whisper / Groq / local-speaches for word-level timestamps.