Add reading lists feature with pinning and management

Adds full support for book lists managed by the Companion App:
- New /list API endpoints (GET/POST) for uploading, retrieving, and deleting lists
- BookListStore for binary serialization of lists to /.lists/ directory
- ListViewActivity for viewing list contents with book thumbnails
- Reading Lists tab in My Library with pin/unpin and delete actions
- Pinnable list shortcut on home screen (split button layout)
- Automatic cleanup of pinned status when lists are deleted

src/activities/home/HomeActivity.h

@@ -26,6 +26,7 @@ class HomeActivity final : public Activity {
   std::string lastBookAuthor;
   std::string coverBmpPath;
   const std::function<void()> onContinueReading;
+  const std::function<void()> onListsOpen;  // Goes to pinned list or lists tab
   const std::function<void()> onMyLibraryOpen;
   const std::function<void()> onSettingsOpen;
   const std::function<void()> onFileTransferOpen;
@@ -41,11 +42,13 @@ class HomeActivity final : public Activity {
 
  public:
   explicit HomeActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
-                        const std::function<void()>& onContinueReading, const std::function<void()>& onMyLibraryOpen,
-                        const std::function<void()>& onSettingsOpen, const std::function<void()>& onFileTransferOpen,
+                        const std::function<void()>& onContinueReading, const std::function<void()>& onListsOpen,
+                        const std::function<void()>& onMyLibraryOpen, const std::function<void()>& onSettingsOpen,
+                        const std::function<void()>& onFileTransferOpen,
                         const std::function<void()>& onOpdsBrowserOpen)
       : Activity("Home", renderer, mappedInput),
         onContinueReading(onContinueReading),
+        onListsOpen(onListsOpen),
         onMyLibraryOpen(onMyLibraryOpen),
         onSettingsOpen(onSettingsOpen),
         onFileTransferOpen(onFileTransferOpen),