feat: transcription module — faster-whisper with ROCm auto-detect

tests/test_transcription.py

@@ -0,0 +1,25 @@
+import asyncio
+from unittest.mock import MagicMock
+
+
+def test_transcription_engine_is_singleton():
+    from transcription import engine, TranscriptionEngine
+    assert isinstance(engine, TranscriptionEngine)
+
+
+def test_transcribe_file_calls_whisper(tmp_path):
+    wav = tmp_path / "test.wav"
+    wav.write_bytes(b"\x00" * 100)
+
+    mock_model = MagicMock()
+    mock_segment = MagicMock()
+    mock_segment.text = " Hallo Welt"
+    mock_model.transcribe.return_value = ([mock_segment], MagicMock())
+
+    from transcription import TranscriptionEngine
+    eng = TranscriptionEngine()
+    eng._model = mock_model
+
+    result = asyncio.run(eng.transcribe_file(str(wav), language="de"))
+    assert result == "Hallo Welt"
+    mock_model.transcribe.assert_called_once_with(str(wav), language="de")