feat(ui): add interactive custom theme configurator

[Reyatsu99]

Description

Adds an interactive Custom Theme Editor to the Preferences menu.

Features

• Live color editing for all ImGui tokens and Prock AppColors.
• Dynamic search filtering to quickly locate specific color properties.
• 'Load Preset' functionality to initialize the custom palette from any built-in theme.
• Persistent saving to the user's INI configuration.

[matrohin]

Hi! I took a look at this PR and I don't think we should merge this. This will get broken for example after upgrading imgui version. So the chosen approach is not sustainable.
I do think that the feature itself can be useful, but this should be designed differently.

If you want, you can create an issue and we can discuss a better design first.
But also I'd be interested to know what specific need do you have? The "Load Preset" part makes me think that maybe there are some wrong colors in the current themes, that we need to fix.
Is this the case?