Reorganize app settings categories

[IgorWarzocha]

Goal

Reorganize app settings so UI/display preferences do not live under the Pi runtime category.

Scope

• Audit current settings categories and identify misplaced settings such as sidebar display options.
• Add or rename a category for app UI/display preferences.
• Move relevant settings into the new structure without changing their stored preference keys.
• Keep existing setting search working for moved settings.

Acceptance criteria

• Sidebar display settings are no longer shown under Pi runtime.
• Runtime settings remain focused on Pi/composer/runtime behavior.
• Moved settings preserve their existing values after the category change.
• Setting titles/descriptions still make sense in their new location.