Fix FastAPI Header import runtime error

backend/main.py

@@ -13,7 +13,7 @@ if _env_file.exists():
             os.environ.setdefault(_k.strip(), _v.strip())
 from datetime import datetime
 
-from fastapi import FastAPI, HTTPException, UploadFile, File, Body
+from fastapi import FastAPI, HTTPException, UploadFile, File, Body, Header
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse, FileResponse
 from fastapi.staticfiles import StaticFiles