修复AI分析SSE流断开：中间件透传Flusher、DB Key生效、错误提示不覆盖

web/backend/internal/handlers/ai.go

@@ -88,7 +88,7 @@ func (d *Deps) Analyze(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Cache-Control", "no-cache")
 	w.Header().Set("Connection", "keep-alive")
 
-	if err := streamLLM(d.AIConfig, prompt, w, flusher); err != nil {
+	if err := streamLLM(llmCfg, prompt, w, flusher); err != nil {
 		log.Printf("[ai] stream error: %v", err)
 		sendSSE(w, flusher, "error", err.Error())
 	}