Feat/password complexity

[rsmithlal]

This pull request introduces password strength validation using the devise_zxcvbn gem and improves internationalization for password-related messages. The most significant changes include adding the new dependency, integrating the module into the user model, and updating translations for password strength feedback in English, Spanish, and French. Minor localization improvements and code comments addressing registration issues are also included.

Password Strength Validation Integration

• Added devise_zxcvbn as a dependency in better_together.gemspec and required it in lib/better_together/engine.rb to enable password strength checking. [1] [2]
• Integrated the :zxcvbnable module into the User model via Devise to enforce strong password requirements.

Internationalization and Localization

• Added new weak_password validation messages in English (config/locales/en.yml), Spanish (config/locales/es.yml), and French (config/locales/fr.yml) to provide clear feedback when a password is too weak. [1] [2] [3]
• Added translations for "password" and corrected locale names in Spanish and French files; also added Ukrainian as a supported locale. [1] [2] [3] [4]

Code Comments and Registration Flow

• Added a comment in the User#person method and a TODO block for weak_words to highlight potential save issues during registration due to automatic association building. [1] [2]