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/Settings/SettingsKey.swift

@@ -66,6 +66,7 @@ enum SettingsKey: String, CaseIterable {
     case homeShortcutVisibility
     case homeShortcutLayout
     case homeShortcutCardStyle
+    case homeShortcutCardColor
     case homeShortcutColorfulPalette
     case homeShortcutCustomPaletteColors
     case homeSectionOrder
@@ -141,7 +142,7 @@ enum SettingsKey: String, CaseIterable {
              .macPlayerSeparateWindow, .macPlayerFloating, .listStyle,
              // Home layout — different UI paradigms per platform
              .homeShortcutOrder, .homeShortcutVisibility, .homeShortcutLayout, .homeShortcutCardStyle,
-             .homeShortcutColorfulPalette, .homeShortcutCustomPaletteColors,
+             .homeShortcutCardColor, .homeShortcutColorfulPalette, .homeShortcutCustomPaletteColors,
              .homeSectionOrder, .homeSectionVisibility, .homeSectionItemsLimit, .homeSectionLayout,
              // Top Shelf — tvOS only
              .topShelfSections,