Remove deprecated user_login, add Holiday API support, and migrate to ruff with Python 3.10 type hints

[ivarurdalen]

Authentication:

• Removed deprecated user_login.py module and associated tests
• Updated ExportApi to use ClientConfig instead of UserLogin

New Features:

• Added Holiday API support with gRPC client and protobuf stubs

Tooling Migration:

• Migrated from pipenv to uv for dependency management (removed Pipfile/Pipfile.lock, added uv.lock)
  Including GitHub workflows.
• Migrated from isort/black/pylint to ruff for code formatting and linting
• Added pre-commit hooks configuration (.pre-commit-config.yaml)
• Consolidated project metadata in pyproject.toml (removed separate VERSION file)

Type Hints:

• Updated codebase to Python 3.10+ style type hints (| for unions and direct use of types)

[jenkins-exabel]

This change is 

[oyvindwe]

@oyvindwe reviewed 163 files and all commit messages, and made 1 comment.
Reviewable status: complete! Pipfile.lock ignored, all files reviewed, all discussions resolved.