Bug: Enforce minimum password length upon registration

### Background Information

Currently, the signup (registration) flow does not enforce a minimum character length for the password field. This can lead to weak passwords, compromising user account security, and not following basic authentication best practices.

### Steps to Reproduce

1. Access the platform.
2. Navigate to the signup (registration) page.
3. Fill all fields.
4. Enter a password with very few characters.
5. Submit the registration form and observe that the user is successfully created.

### How

Implement a minimum character length validation for the password field during user registration.

### Expected Behavior

The system should prevent user registration when the password does not meet the minimum character requirement and display a clear validation message informing the user about the password rules.