STT-Dienst: Kern, HTTP/WebSocket/Wyoming-Service, CLI, Tests, systemd-Unit

- stt_core.py: Whisper-Engine (einmal laden, CPU-Fallback), Audio-Dekodierung
  jedes Formats, Halluzinationsfilter, Äußerungserkennung per Silero-VAD
- stt_service.py: /health, /v1/audio/transcriptions (OpenAI), /transcribe (Rohdaten),
  WS /ws/stream; Inferenz im Worker-Thread, begrenzte Warteschlange (503)
- stt_wyoming.py: Home-Assistant-Anbindung (TCP 10300)
- stt_cli.py: Datei/Mikrofon über den Dienst oder lokal
- Tests (Unit + Integration), README, requirements.txt, deploy/stt-service.service

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

pytest.ini

@@ -0,0 +1,6 @@
+[pytest]
+testpaths = tests
+markers =
+    integration: echtes Whisper-Modell (langsamer, braucht gecachtes Modell)
+addopts = -m "not integration"
+asyncio_default_fixture_loop_scope = function