Security: Sanitize User-Supplied GitHub URL in `get` Command

Feature Request

Is your feature request related to a problem you're trying to solve with Universal-Box? Please describe. Currently, the get command accepts a GitHub repository URL directly from the user. Without validation, it could allow malformed or malicious URLs (e.g., command injections, non-GitHub domains, or scripts), potentially causing security issues or unexpected behavior.

Describe the solution you'd like Implement strict input sanitization and validation for user-supplied URLs in the get command:

• Allow only valid GitHub repository URLs (https://github.com/{user}/{repo} or https://www.github.com/{user}/{repo}).
• Reject URLs with query parameters, special characters, or other schemes (file://, ftp://, etc.).
• Use a regex-based or URL-parsing validation approach to ensure the URL structure and domain integrity.

Describe alternatives you've considered

• Whitelisting specific domains (only github.com and www.github.com).
• Escaping user input before shell execution.
• Requiring a token-authenticated fetch instead of direct URL usage.

How would this feature improve Universal-Box? Enhances security and reliability of the get command by preventing misuse, accidental errors, and potential injection vectors. This ensures Universal-Box safely handles user input without compromising on developer convenience.

Additional context This validation step can be placed before cloning logic in the get command workflow. Optionally, a --force flag could bypass validation (for internal or advanced usage).