fix: Update exclusion codespell linting artifacts

What does this merge request do and why?

1. Log files should be excluded because:

   • They're runtime artifacts, not source code
   • They often contain truncated/malformed text from error messages
   • Already listed in .gitignore

2. Protobuf files should be excluded because:

   • They're generated code, not manually written
   • They may contain encoded/binary-like text patterns
   • They're already partially handled (pylint ignores them)
   • Node modules and .venv protobuf files are already skipped by directory exclusions

3. Sorted alphabetically for easier maintenance

How to set up and validate locally

• poetry run codespell ai-gateway.log # Should skip the file
• poetry run codespell contract/contract_pb2.py # Should skip the file
• make check-codespell # Should pass without log/protobuf false positives

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.
• If this change requires executor implementation: verified that issues/MRs exist for both Go executor and Node executor or confirmed that changes are backward-compatible and don't break existing executor functionality.