Add configurable quick color palette

[devmobasa]

Summary

Resolves #262.

Adds a configurable quick color palette via ordered [[drawing.quick_colors]] entries. Each entry can define a label and color, with support for named colors, RGB arrays, and #RRGGBB hex values.

The first eight entries continue to map to the existing quick color actions and shortcuts:

R / G / B / Y / O / P / W / K

Additional entries are palette-only colors with no shortcut action binding.

Behavior

• Existing quick color action names are unchanged.
• Existing configs continue to work.
• Missing or omitted quick colors fall back to built-in defaults.
• Short custom palettes backfill missing shortcut slots from defaults.
• Default toolbar/radial behavior is preserved for users who do not customize quick colors.
• Cyan, Purple, and Gray remain available as expanded toolbar colors.
• Dense palette surfaces cap rendered quick colors at 24 entries.

UI / Configurator

Adds configurator support for quick colors:

• edit labels
• edit named, hex, or RGB colors
• add/remove/reorder entries
• validate quick-color color inputs
• warn when entries exceed the rendered palette limit

The runtime quick color palette is now shared by input actions, toolbar rendering, help badges, and radial menu color rendering/dispatch.