feat(asr): refactor OpenAI ASR integration, add Deepgram/OpenAI ASR adapters, and polish provider tests

[tavinashb]

• This approach enables the OpenAI client to support both chat and ASR APIs through a single instance.
• Refactors ASR provider integration to introduce adapters and cleaner provider wiring.
• Updates OpenAI ASR provider integration and Deepgram ASR provider adapters.
• Improves portability of audio file handling and validation logic for ASR providers.
• Cleans up unused imports and refactors types for ASR-related modules.
• Updates unit tests to cover OpenAI ASR and Deepgram flows and fixes client tests for ASR support.