feat(stt): add keyterms parameter in Elevenlabs STT plugin

[Arjun-A-I]

Summary

• Add keyterms parameter to ElevenLabs STT plugin for batch recognition, allowing users to bias transcription towards specific words or phrases (e.g. product names, technical terms)
• Supported on Scribe v2 models only (not realtime streaming), matching the ElevenLabs API specification
• Also exposed via update_options() for runtime updates

Related Elevenlabs API Docs :

• https://elevenlabs.io/docs/api-reference/speech-to-text/convert#request.body.keyterms.keyterms

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[devin-ai-integration]

✅ Devin Review: No Issues Found

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[Arjun-A-I]

@theomonnom can you take a look