Enhanced Password Generator UX: added copy button, password length input, and theme toggle labels

[JayeshSh1602]

Summary

This PR improves the user experience for the Password Generator project. It addresses the suggestions mentioned in issue #180 by adding a few useful features and small UI fixes.

Changes Made

• Added a password length input field so users can choose custom password lengths (6–32).
• Added Copy buttons next to each generated password with visual feedback ("Copied!").
• Added a label for the theme toggle to improve accessibility and clarity.
• Fixed label visibility in dark mode (both "Password length" and "Toggle Theme" are now readable in both themes).
• Slight HTML cleanup (removed duplicate IDs and improved structure).

Testing

• Tested in both dark and light modes.
• Verified password generation, length control, and copy functionality all work correctly.

Issue Reference

Fixes #180

---

Let me know if any further tweaks are needed! 😊