Colorful shortcut cards now color by grid position instead of shortcut
identity, so colors stay in the same slot when shortcuts are reordered.
Adds a Palette option (Classic default, plus Sunset, Meadow, Berry,
Grape) and a Custom palette with a swatch-list editor (ColorPicker + hex
fields) and a switchable comma-separated text field. Color is resolved
per position and wraps by palette length, wired via a new
homeShortcutColorfulColor environment value and a Color(hex:) extension.
Replace the inline Plain/Accent/Colorful picker in Home customization with
a navigation row that opens a dedicated page. The new page keeps the style
selector and renders a non-interactive preview of every shortcut type so
the chosen style is visible before committing.
- Add an optional styleOverride to HomeShortcutCardView so the preview can
reflect the not-yet-saved selection.
- On macOS, navigate via navigationDestination(isPresented:) instead of a
List-embedded NavigationLink, which otherwise stays stuck in its selected
state after popping back and can't be reopened.
