Add a Two-Factor Authentication (2FA) section to the Contractor Portal Settings, allowing contractors to enable, disable, and manage 2FA for their accounts. The setup and login flow should be consistent with the Agency Portal implementation.

Acceptance Criteria:

• Contractors can enable and disable 2FA.
• Verification is required during setup.
• Users with 2FA enabled are prompted for a verification code during login.
• The current 2FA status is displayed in Settings.