Reject booleans for numeric configuration fields

[sylvesterkaczmarek]

Fixes #15.

Python booleans are subclasses of int, so the generic numeric validators accepted True for fields such as max_workers and padding_factor.

Reject booleans explicitly in both integer and numeric validation while preserving the existing error messages.

Validation:

• pytest tests/cutana/unit/test_validate_config.py -q — 49 passed
• pytest tests/cutana/unit -q — 531 passed, 6 skipped
• ruff check cutana/validate_config.py tests/cutana/unit/test_validate_config.py
• ruff format --check cutana/validate_config.py tests/cutana/unit/test_validate_config.py
• git diff --check