feat：添加对话情景功能

backend/internal/orchestrator/pipeline.go

@@ -193,12 +193,13 @@ func (p *Pipeline) ProcessQuery(
 	})
 
 	// Step 2+3: LLM 流式推理 + TTS 并行合成
-	log.Infow("开始 LLM 推理", "request_id", req.RequestID)
+	log.Infow("开始 LLM 推理", "request_id", req.RequestID, "scenario", sess.Config.Scenario)
 	llmReq := llm.Request{
-		Image:    image,
-		Text:     userText,
-		History:  history,
-		Language: sess.Config.Language,
+		Image:        image,
+		Text:         userText,
+		History:      history,
+		Language:     sess.Config.Language,
+		SystemPrompt: llm.GetScenarioPrompt(sess.Config.Scenario, sess.Config.Language),
 	}
 
 	llmStream, err := p.llmService.ChatStream(ctx, llmReq)