Split home shortcut card style into Layout, Color, and Palette

Decouple the two concerns that were entangled in a single card-style setting:

- Layout (Compact / Regular) now only controls positioning of the
  icon / title / subtitle / counter.
- Color (Soft / Vibrant) is a new independent setting: Soft = tinted
  background with palette-colored icon and neutral text; Vibrant =
  solid palette fill with white icon/text.
- Palette (Accent first, then Classic/Sunset/Meadow/Berry/Grape/Custom)
  now applies to both layouts and both colors, and is always shown.

Adds section headers (Layout / Color / Palette) to the style page and
fixes the Compact preview to show the count subtitle line. Default is
Regular + Soft + Accent.

Yattee/Core/SettingsManager.swift

@@ -110,6 +110,7 @@ final class SettingsManager {
     var _homeShortcutVisibility: [HomeShortcutItem: Bool]?
     var _homeShortcutLayout: HomeShortcutLayout?
     var _homeShortcutCardStyle: HomeShortcutCardStyle?
+    var _homeShortcutCardColor: HomeShortcutCardColor?
     var _homeShortcutColorfulPalette: HomeShortcutColorfulPalette?
     var _homeShortcutCustomPaletteColors: [String]?
     var _homeSectionOrder: [HomeSectionItem]?
@@ -469,6 +470,7 @@ final class SettingsManager {
         _homeShortcutVisibility = nil
         _homeShortcutLayout = nil
         _homeShortcutCardStyle = nil
+        _homeShortcutCardColor = nil
         _homeShortcutColorfulPalette = nil
         _homeShortcutCustomPaletteColors = nil
         _homeSectionOrder = nil