HU-02: Reject ASCII control characters in quoted email local parts - #520

HU-02: ASCII Control Character Validation

Description

Improves email validation by rejecting ASCII control characters in quoted local parts.

Changes

• Replaced the original SOH-specific test with a parametrized test covering 9 ASCII control character cases, including SOH.
• Updated the regular expression in src/validators/email.py to reject these control characters.
• Verified that the behavior of the 95 printable ASCII characters evaluated remains unchanged.

TDD Process

• RED: The 9 parametrized tests failed before modifying the implementation.
• GREEN: All 9 tests passed after updating the regular expression.
• REFACTOR: Reviewed the implementation and confirmed that no additional refactoring was necessary.

Validation Results

• 9 parametrized tests passed.
• Existing email regression tests passed.
• Ruff static analysis: All checks passed!.
• Full test suite: 1122 passed, 4 failed.

The 4 remaining failures were already present before this change and correspond to other pending functionalities.