Add cookie file upload

tests/test_web_app.py

@@ -5,7 +5,13 @@ from __future__ import annotations
 import sys
 
 import web_app
-from web_app import build_pipeline_command, create_app, load_translation_settings, save_translation_settings
+from web_app import (
+    _stage_uploaded_cookies,
+    build_pipeline_command,
+    create_app,
+    load_translation_settings,
+    save_translation_settings,
+)
 
 
 def test_build_pipeline_command_uses_cli_parser_defaults():
@@ -91,3 +97,29 @@ def test_load_translation_settings_uses_env_defaults(tmp_path, monkeypatch):
         "api_key": "env-key",
         "model": "env-model",
     }
+
+
+def test_stage_uploaded_cookies_copies_to_upload_dir(tmp_path, monkeypatch):
+    upload_dir = tmp_path / "uploads"
+    source_file = tmp_path / "cookies.txt"
+    source_file.write_text("# Netscape HTTP Cookie File\n", encoding="utf-8")
+    monkeypatch.setattr(web_app, "UPLOAD_DIR", upload_dir)
+
+    staged_path = _stage_uploaded_cookies(str(source_file))
+
+    assert staged_path.endswith(".txt")
+    assert staged_path != str(source_file)
+    assert upload_dir in web_app.Path(staged_path).parents
+    assert web_app.Path(staged_path).read_text(encoding="utf-8") == "# Netscape HTTP Cookie File\n"
+
+
+def test_stage_uploaded_cookies_rejects_unsupported_extension(tmp_path):
+    source_file = tmp_path / "cookies.json"
+    source_file.write_text("{}", encoding="utf-8")
+
+    try:
+        _stage_uploaded_cookies(str(source_file))
+    except ValueError as exc:
+        assert "Expected one of" in str(exc)
+    else:
+        raise AssertionError("Expected ValueError for unsupported cookie upload")