UI Cut 01: remove fake theme split and trim kit dead weight

[DerpcatMusic]

What changed

• remove the fake native/custom style split from the theme path
• simplify brand and kit theme resolution to one real rendering path
• delete and the no-op native shadow helper
• replace the map GPS FAB with a plain pressable
• add the consolidated brutal UI/UX audit document

Why

The UI layer was carrying fake flexibility and dead kit primitives that increased complexity without improving the product. This is the first cleanup slice before cutting home/jobs chrome.

Verification