Feature/modularization

[KoreAustralian]

Description

This PR modularizes the main game logic in cargame.py into separate files to improve code readability, maintainability, and scalability. Specifically, the Game class is moved to game_logic.py, background code is moved to draw_background.py, and asset-loading functions are extracted into assets.py.

Type of change

• [ V ] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Manually tested the game via python main.py to ensure full functionality.
Verified that background rendering, score display, and car movement behave as expected after modularization.
Confirmed that the game runs without errors and the dashed lines animate correctly.

Checklist:

• [ V ] I have followed the coding style guidelines of this project
• [ V ] I have reviewed my own code
• I have commented hard-to-understand areas of my code
• I have added docstrings to all public functions/methods
• [ V ] I have used descriptive variable names to make by code easier to understand
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Related Issue(s)

Closes #46