[WIP] Optimize Python program for improved performance and efficiency

[Copilot]

• Optimize zombie.py: Use dictionary lookups for zombie/NPC position checks (O(1) instead of O(n))
• Optimize zombie.py: Cache font object for flagged zombie rendering instead of creating new font each frame
• Optimize zombie.py: Cache win condition state instead of recalculating every frame
• Optimize player.py: Combine redundant key checks for movement
• Optimize helper.py: Cache text surface in Button class to avoid re-rendering on every frame
• Optimize screens/play_board.py: Cache grid surface instead of recreating each frame
• Run code review and security checks

Original prompt

Optimize the Python program in the repository for improved performance and efficiency. Do not add any comments to the code during the optimization process. Only focus on optimizations related to code execution speed, resource usage, and algorithmic improvements.

This pull request was created as a result of the following prompt from Copilot chat.

Optimize the Python program in the repository for improved performance and efficiency. Do not add any comments to the code during the optimization process. Only focus on optimizations related to code execution speed, resource usage, and algorithmic improvements.

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