Revert Claude : retour au stub Qwen — interface stable, branchement à venir

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/routers/qualify.py

@@ -25,7 +25,7 @@ from app.services.qualify_ai_service import (
     AIMessage,
     AIQuestion,
     AIQualifyResult,
-    ai_frame_async,
+    ai_frame,
 )
 
 router = APIRouter()
@@ -127,7 +127,7 @@ async def ai_chat(payload: AIChatRequest) -> AIChatResponse:
         context=payload.context,
         messages=[AIMessage(role=m.role, content=m.content) for m in payload.messages],
     )
-    resp = await ai_frame_async(req)
+    resp = ai_frame(req)
 
     return AIChatResponse(
         done=resp.done,