Add password strength validation (min 8 chars, 1 uppercase, 1 number)

[volcodes]

Enhance security by implementing password strength validation rules to ensure users create strong passwords. The requirements are as follows: a minimum of 8 characters, at least 1 uppercase letter, and at least 1 numeric digit.

Acceptance Criteria:

• Develop a utility function to validate password strength based on the specified rules:
  • Minimum of 8 characters.
  • At least 1 uppercase letter.
  • At least 1 numeric digit.
• Integrate the password validation function into the user registration and password update workflows.
• Provide user-friendly error messages for each validation failure (e.g., "Password must contain at least 8 characters").
• Write unit tests to ensure validation works for various valid and invalid password scenarios.
• Ensure the existing functionality is not impacted by the new validation.
• Make sure this issue closes;
  • Create password hash logic #6
  • Implement password hashing using bcrypt #12
  • Implement bcrypt password comparison at login #17

Technical Notes:

• Use regexp from the standard Go library for pattern matching.
• Follow project conventions for error handling and localization of error messages, if applicable.
• Make the validation reusable for future password-related features.