fix(stt): pass language to groq transcription

[hashbender]

Summary

• pass language to Groq Whisper transcription requests when configured
• prefer stt.groq.language, falling back to stt.local.language and the existing local STT language env
• add regression coverage for Groq-specific language and local fallback behavior

Fixes NousResearch#55551

Tests

• .venv/bin/python -m pytest tests/tools/test_transcription_tools.py -q -k "TranscribeGroq or groq_language"
• .venv/bin/python -m ruff check tools/transcription_tools.py tests/tools/test_transcription_tools.py
• .venv/bin/python -m pytest tests/tools/test_transcription_tools.py -q
• scripts/run_tests.sh tests/tools/test_transcription_tools.py -q

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Mirror-of: NousResearch#57173
NousResearch#57173