Fix Home card style selection not persisting

The Home settings screen copies settings into local @State on appear and
saves on disappear. Pushing the card style page fired onDisappear (saving
pre-edit values), and popping back re-ran loadSettings, clobbering the
style just edited through the bindings — so the selection reverted.

Load settings only once per presentation, and persist style, palette, and
custom colors immediately from the style page via an onSave callback. The
owning view sits covered in the navigation stack where its own onChange
never fires, and swipe-dismissing the settings sheet from the style page
skips its lifecycle entirely, so saving must happen from the visible child.

Yattee/Views/Home/HomeShortcutStyleView.swift

@@ -14,6 +14,11 @@ struct HomeShortcutStyleView: View {
     @Binding var palette: HomeShortcutColorfulPalette
     @Binding var customColors: [String]
 
+    /// Called after any value changes so the owner persists immediately. The
+    /// owner sits covered in the navigation stack where its own onChange never
+    /// fires, and swipe-dismissing the sheet from here skips its lifecycle.
+    var onSave: (() -> Void)? = nil
+
     /// Editing mode for the custom palette.
     private enum CustomEditMode: String, CaseIterable {
         case list
@@ -87,6 +92,9 @@ struct HomeShortcutStyleView: View {
         #if os(iOS)
         .navigationBarTitleDisplayMode(.inline)
         #endif
+        .onChange(of: style) { onSave?() }
+        .onChange(of: palette) { onSave?() }
+        .onChange(of: customColors) { onSave?() }
     }
 
     // MARK: - Palette