Java GUI Login/Register System v1.0

Initial release of a complete Java Swing Login & Registration System.

🔐 Features:

• Password hashing (SHA-256)
• Email domain validation (Gmail, Outlook, YahooMail, Hotmail)
• Duplicate username check
• Dark Mode toggle
• Welcome screen with logout
• File-based storage (users.txt)

Built with pure Java and Swing – no external libraries required.