fix: use relative imports for python files

backend/routes/shortener.py

@@ -1,11 +1,11 @@
 from fastapi import APIRouter, HTTPException
 from fastapi.responses import RedirectResponse
 
-from backend.db import database
-from backend.exceptions import ShortcodeNotFound, ShortcodeConflict
-from backend.utils import encoder
-from backend.schemas import UrlPayload
-from backend.services import UrlService
+from ..db import database
+from ..exceptions import ShortcodeNotFound, ShortcodeConflict
+from ..utils import encoder
+from ..schemas import UrlPayload
+from ..services import UrlService
 
 router = APIRouter()
 url_service = UrlService(db=database)