feat: Konversationsgedaechtnis - Kurzzeit-Gespraechsverlauf pro Session

- Store: messages-Tabelle + append_message/get_recent_messages (mit Mandanten-Schutz)
- LLMProvider.complete um history erweitert (openrouter + local bauen system+history+user)
- Orchestrator.chat_text reicht den Verlauf ans LLM weiter
- chat.py: bei session_id letzte HISTORY_MAX_MESSAGES laden, danach User-/Assistant-Turn speichern
- ohne session_id weiterhin zustandslos; ?debug zeigt history_len
- Config HISTORY_MAX_MESSAGES (Default 10)
- Tests: 32 gruen (3 neue Gedaechtnis-Tests)
- Doku aktualisiert (README, BEDIENUNGSANLEITUNG, Architektur)

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

app/api/chat.py

@@ -11,6 +11,7 @@ from app.dependencies import (
     resolve_route,
     build_orchestrator,
     resolve_output_endpoint,
+    get_store,
 )
 from app.schemas import ChatRequest
 
@@ -50,10 +51,18 @@ async def chat(
     }
     voice = payload.voice or settings.openrouter_tts_voice
 
+    store = get_store()
+
     try:
         route = resolve_route(user, session_id, overrides)
         orchestrator = build_orchestrator(route)
         output = await resolve_output_endpoint(route)
+        # Gespraechsverlauf laden (nur bei gesetzter session_id -> sonst zustandslos).
+        history = (
+            store.get_recent_messages(session_id, settings.history_max_messages)
+            if session_id
+            else []
+        )
     except SessionOwnershipError as exc:
         raise HTTPException(status_code=403, detail=str(exc))
     except RoutingError as exc:
@@ -65,33 +74,39 @@ async def chat(
             language=route.language,
             voice=voice,
             output=output,
+            history=history,
         )
-
-        if debug:
-            return JSONResponse(
-                content={
-                    "ok": True,
-                    "voice": voice,
-                    "route": route.as_dict(),
-                    "trace": {
-                        "raw_transcript": trace.raw_transcript,
-                        "cleaned_transcript": trace.cleaned_transcript,
-                        "semantic_response": trace.semantic_response,
-                        "spoken_response": trace.spoken_response,
-                        "tts_ready_text": trace.tts_ready_text,
-                    },
-                }
-            )
-
-        headers = {
-            "Content-Language": route.language,
-            "X-Audio-Format": "pcm",
-            "X-Audio-Sample-Rate": "24000",
-            "X-Audio-Channels": "1",
-            "X-Audio-Sample-Width": "16",
-            **_route_headers(route),
-        }
-        return StreamingResponse(BytesIO(audio), media_type="audio/pcm", headers=headers)
-
     except Exception as exc:
         raise HTTPException(status_code=502, detail=str(exc))
+
+    # Turn persistieren (User-Eingabe + semantische Antwort) fuer das Gedaechtnis.
+    if session_id:
+        store.append_message(session_id, user.id, "user", payload.text)
+        store.append_message(session_id, user.id, "assistant", trace.semantic_response)
+
+    if debug:
+        return JSONResponse(
+            content={
+                "ok": True,
+                "voice": voice,
+                "route": route.as_dict(),
+                "history_len": len(history),
+                "trace": {
+                    "raw_transcript": trace.raw_transcript,
+                    "cleaned_transcript": trace.cleaned_transcript,
+                    "semantic_response": trace.semantic_response,
+                    "spoken_response": trace.spoken_response,
+                    "tts_ready_text": trace.tts_ready_text,
+                },
+            }
+        )
+
+    headers = {
+        "Content-Language": route.language,
+        "X-Audio-Format": "pcm",
+        "X-Audio-Sample-Rate": "24000",
+        "X-Audio-Channels": "1",
+        "X-Audio-Sample-Width": "16",
+        **_route_headers(route),
+    }
+    return StreamingResponse(BytesIO(audio), media_type="audio/pcm", headers=headers)