[DevTask] Move colorPalettes to core

Currently `colorPalette` is a core extension, however there are already code in the core that depends on the colorPalette, which makes it impossible to turn off the extension while keep other part running. We should just move colorPaletes to core.

The storage of colorPalettes should be handled by Pinia and the management UI should be rewritten with Vue.

Locate the colorPalette extension, the core code that depends on it, and the existing management UI. Review how color palettes are currently stored, then plan the move into core with Pinia-backed storage and a Vue management UI. Done means core no longer depends on an optional colorPalette extension and the palette UI still manages the same data.

Written by the indexing model from the issue text.