feat: 完善后端知识库服务和配置

- 优化 AI-Core 客户端调用
- 添加更多知识库配置选项
- 完善文档解析逻辑

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

server/cmd/api/main.go

@@ -87,7 +87,7 @@ func main() {
 	if err != nil {
 		log.Printf("Warning: Failed to initialize upload service: %v (files will not be available)", err)
 	}
-	knowledgeService := service.NewKnowledgeService(knowledgeRepo, modelRepo, uploadService, cfg.PythonServiceURL, cfg.AICoreServiceAddr)
+	knowledgeService := service.NewKnowledgeService(knowledgeRepo, modelRepo, uploadService, cfg.PythonServiceURL, cfg.AICoreServiceAddr, cfg.MarkdownLocalPath)
 
 	// 6. 初始化 Handler
 	dbHandler := handler.NewDatabaseHandler(dbService)