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/audio/router.py

@@ -0,0 +1,38 @@
+from app.errors import UnknownEndpointError
+
+
+class AudioRouter:
+    def __init__(self, inputs, outputs):
+        self.inputs = inputs
+        self.outputs = outputs
+
+    async def list_inputs(self):
+        return [await endpoint.capabilities() for endpoint in self.inputs]
+
+    async def list_outputs(self):
+        return [await endpoint.capabilities() for endpoint in self.outputs]
+
+    async def select_input(self, preferred: str | None = None):
+        return await self._select(self.inputs, preferred, direction="input")
+
+    async def select_output(self, preferred: str | None = None):
+        return await self._select(self.outputs, preferred, direction="output")
+
+    async def _select(self, endpoints, preferred: str | None, direction: str):
+        # Capabilities einmal sammeln (Basis fuer spaetere capability-basierte Auswahl).
+        pairs = [(endpoint, await endpoint.capabilities()) for endpoint in endpoints]
+
+        if preferred:
+            for endpoint, caps in pairs:
+                if caps.id == preferred or caps.kind == preferred:
+                    return endpoint
+            # Angefragter Endpunkt existiert nicht -> KEIN stiller Default-Fallback.
+            available = sorted({caps.id for _, caps in pairs} | {caps.kind for _, caps in pairs})
+            raise UnknownEndpointError(
+                f"Unbekannter {direction}-Endpunkt {preferred!r}. Verfuegbar: {available}"
+            )
+
+        for endpoint, caps in pairs:
+            if caps.default:
+                return endpoint
+        raise RuntimeError(f"Kein {direction}-Standardendpunkt verfuegbar")