feat(scraper): add login stubs for codechef, kattis, usaco

scrapers/codechef.py

@@ -13,6 +13,7 @@ from .timeouts import HTTP_TIMEOUT
 from .models import (
     ContestListResult,
     ContestSummary,
+    LoginResult,
     MetadataResult,
     ProblemSummary,
     SubmitResult,
@@ -267,6 +268,9 @@ class CodeChefScraper(BaseScraper):
             verdict="",
         )
 
+    async def login(self, credentials: dict[str, str]) -> LoginResult:
+        return self._login_error("CodeChef login not yet implemented")
+
 
 if __name__ == "__main__":
     CodeChefScraper().run_cli()