fix: 500 error when downloading projects with non-ASCII characters (ex. Cyrillic) names (#8483)

* fix: encode Cyrillic filenames in Content-Disposition header

* [autofix.ci] apply automated fixes

---------

Co-authored-by: Ilia Krupin <ilia.krupin@tedo.ru>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Gabriel Luiz Freitas Almeida <gabriel@langflow.org>

src/backend/base/langflow/api/v1/projects.py

@@ -3,6 +3,7 @@ import json
 import zipfile
 from datetime import datetime, timezone
 from typing import Annotated
+from urllib.parse import quote
 from uuid import UUID
 
 import orjson
@@ -292,17 +293,20 @@ async def download_file(
         with zipfile.ZipFile(zip_stream, "w") as zip_file:
             for flow in flows_without_api_keys:
                 flow_json = json.dumps(jsonable_encoder(flow))
-                zip_file.writestr(f"{flow['name']}.json", flow_json)
+                zip_file.writestr(f"{flow['name']}.json", flow_json.encode("utf-8"))
 
         zip_stream.seek(0)
 
         current_time = datetime.now(tz=timezone.utc).astimezone().strftime("%Y%m%d_%H%M%S")
         filename = f"{current_time}_{project.name}_flows.zip"
 
+        # URL encode filename handle non-ASCII (ex. Cyrillic)
+        encoded_filename = quote(filename)
+
         return StreamingResponse(
             zip_stream,
             media_type="application/x-zip-compressed",
-            headers={"Content-Disposition": f"attachment; filename={filename}"},
+            headers={"Content-Disposition": f"attachment; filename*=UTF-8''{encoded_filename}"},
         )
 
     except Exception as e: