Refactor music player into class-based structure for better maintainability

[Tithi234]

Summary

This PR refactors the music player from a procedural script
into a class-based structure to improve maintainability,
organization, and scalability.

Changes Made

• Wrapped application logic inside a MelodyPlayer class
• Replaced global variables with instance attributes
• Encapsulated UI setup inside class methods
• Preserved all existing functionality
• Improved code organization and readability

Why This Change?

The previous implementation relied heavily on global state and
top-level functions, which made the code harder to extend and maintain.

Moving to a class-based design:

• Reduces global variable usage
• Improves encapsulation
• Makes the project more scalable
• Aligns with standard Python project structure

Impact

No changes to user-facing functionality.
The application behavior remains the same.
This is purely a structural improvement.

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