feat: port crossink 'read book move' feature to crosspoint (#2032)

src/activities/reader/EpubReaderActivity.h

@@ -31,6 +31,9 @@ class EpubReaderActivity final : public Activity {
   bool pendingSyncSaveError = false;
   bool skipNextButtonCheck = false;  // Skip button processing for one frame after subactivity exit
   bool automaticPageTurnActive = false;
+  // Set when the reader is left at end-of-book and SETTINGS.moveFinishedToReadFolder is on.
+  // Consumed in onExit() to relocate the finished book into /Read/.
+  bool pendingReadFolderMove = false;
 
   // Footnote support
   std::vector<FootnoteEntry> currentPageFootnotes;