refactor(esx_dmvschool): code structure

[ghost]

Description

• Centralize TextUI display/hide functions (ShowDMVTextUI / HideDMVTextUI)
• Remove duplicated code when opening/closing the menu
• Ensure TextUI only shows when inside DMVSchool zone
• Automatically hide TextUI when menu opens and show it when menu closes if still in zone
• Clean up code for better readability and maintainability

PR Checklist

• My commit messages and PR title follow the Conventional Commits standard.
• My changes have been tested locally and function as expected.
• My PR does not introduce any breaking changes.
• I have provided a clear explanation of what my PR does, including the reasoning behind the changes and any relevant context.

[zRxnx]

Thats not german

[N0tNvll]

Make that the system have a better readable in client side pls
At the same time i continue seeing some parts of the code that can be refactorize

[CLAassistant]

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