ui: only import layouts that are used

[TheSecurityDev]

Avoid the overhead of loading all the big UI layouts on mici and vice-versa.

[Copilot]

Pull Request Overview

This PR optimizes UI module loading by moving layout imports from module-level to conditional imports within the main() function. This ensures that only the relevant UI layout (MainLayout for TICI/TIZI devices, or MiciMainLayout for smaller devices) is loaded based on the hardware type, avoiding the overhead of importing unused large UI modules.

Key changes:

• Removed top-level imports of MainLayout and MiciMainLayout
• Added conditional imports inside main() based on gui_app.big_ui() check

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[github-actions]

raylib UI Preview

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[TheSecurityDev]

Will update to do this for setup, updater, reset layout imports also

[adeebshihadeh]

Does this actually make a difference? You can check with PROFILE_STARTUP=1.

[TheSecurityDev]

Does this actually make a difference? You can check with PROFILE_STARTUP=1.

I can't find any measurable startup speed difference. Using memory-profiler shows a couple MB of memory savings. It just seemed the logical thing to do, but maybe it's not necessary.

[adeebshihadeh]

If it makes zero difference, this PR has been a net negative to this project. Please go through your PRs and close any that look like this.

Focus on the things that you and others will notice! That can be both developer or user experience. Like these are two good ones: #36570 & https://github.com/commaai/openpilot/pull/36647/files.