feat: Add settings to control play button visibility on home shelves

This commit introduces new functionality to customize the visibility of the
play button on home page shelves.

Key changes:

- Added `HomePageSettings` to `AppSettings` to store your preferences:
    - `showPlayButtonOnContinueShelves`: Controls visibility on "Continue Listening" and "Continue Series" shelves (default: true).
    - `showPlayButtonOnAllShelves`: Controls visibility on other shelves (default: false).
- Modified `BookHomeShelf` to respect these settings when rendering books.
- Created a new "Home Page Settings" page under "Appearance" in App Settings, allowing you to toggle these two options.
- Added comprehensive unit and widget tests to cover the new settings model, the conditional logic in `BookHomeShelf`, and the functionality of the new settings page.

lib/router/constants.dart

@@ -52,6 +52,11 @@ class Routes {
     name: 'shakeDetectorSettings',
     parentRoute: settings,
   );
+  static const homePageSettings = _SimpleRoute(
+    pathName: 'home-page',
+    name: 'homePageSettings',
+    parentRoute: settings,
+  );
 
   // search and explore
   static const search = _SimpleRoute(