A redesigned create workspace

The create page is now a tabbed workspace: style, colours, and fine-tune share one rail beside the live map, with light, dark, and compare preview modes and a single Use theme button.

• Style, colours, and fine-tune are tabs in one rail now, with the live map and the export code beside them instead of behind a step accordion.
• Switch the map preview between light only, dark only, or light and dark side by side.
• Pick a style or a colour palette from visual thumbnails instead of a text list.