Initial commit: Voice Assistant Gateway mit Konfig-/Routing-Fundament

- FastAPI-Gateway mit REST-Endpunkten (chat/speak/transcribe/devices/sessions/config)
- Geschichtete Konfiguration mit Profilen (local-dev/hybrid/cloud) via TOML + ENV
- Registry-Pattern + einheitliche Route-Aufloesung (Default->Profil->ENV->Session->Request)
- Device Router (strikt, Singleton) und Output-Lifecycle im Orchestrator
- OpenRouter-Adapter (STT multipart/LLM/TTS) + lokale Provider-Stubs
- Regelbasierte Pipeline (Cleaner/Spoken-Adapter/TTS-Normalizer)
- 22 automatisierte Tests; Doku: README, BEDIENUNGSANLEITUNG, Architektur
- Secrets ausschliesslich ueber Umgebung; .env und lokale config gitignored

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/providers/stt/openrouter.py

@@ -0,0 +1,46 @@
+import httpx
+
+from app.providers.stt.base import STTProvider
+
+
+class OpenRouterSTTProvider(STTProvider):
+    def __init__(self, api_key: str, model: str):
+        self.api_key = (api_key or "").strip()
+        self.model = (model or "").strip()
+
+    async def transcribe(self, audio_bytes: bytes, fmt: str, language: str | None = None) -> str:
+        if not self.api_key:
+            raise ValueError("OPENROUTER_API_KEY is empty")
+        if not self.model:
+            raise ValueError("OPENROUTER_STT_MODEL is empty")
+        if not audio_bytes:
+            raise ValueError("STT input audio is empty")
+
+        # OpenAI-kompatibler /audio/transcriptions-Endpunkt erwartet multipart/form-data
+        # mit binärem file-Feld, nicht JSON mit base64.
+        files = {"file": (f"audio.{fmt}", audio_bytes, f"audio/{fmt}")}
+        data: dict[str, str] = {"model": self.model}
+        if language:
+            data["language"] = language
+
+        timeout = httpx.Timeout(connect=10.0, read=120.0, write=30.0, pool=10.0)
+
+        async with httpx.AsyncClient(timeout=timeout) as client:
+            try:
+                response = await client.post(
+                    "https://openrouter.ai/api/v1/audio/transcriptions",
+                    headers={"Authorization": f"Bearer {self.api_key}"},
+                    files=files,
+                    data=data,
+                )
+                response.raise_for_status()
+            except httpx.HTTPStatusError as exc:
+                raise RuntimeError(
+                    f"OpenRouter STT error {exc.response.status_code}: {exc.response.text}"
+                ) from exc
+            except httpx.TimeoutException as exc:
+                raise RuntimeError("OpenRouter STT timeout") from exc
+            except httpx.HTTPError as exc:
+                raise RuntimeError(f"OpenRouter STT transport error: {exc}") from exc
+
+        return response.json().get("text", "")