Fix: Preserve page number when rotating screen

Previously, rotating the screen would reset the reading position to the beginning of the chapter. This change ensures the current page number is stored and restored after the view re-renders.

src/activities/reader/EpubReaderActivity.cpp

@@ -512,6 +512,11 @@ void EpubReaderActivity::rotateScreen() {
   // We don't want to change orientation mid-render, so grab the semaphore
   xSemaphoreTake(renderingMutex, portMAX_DELAY);
 
+  // If a section is loaded, preserve the current page number
+  if (section) {
+    nextPageNumber = section->currentPage;
+  }
+
   //
   // Cycle to next orientation
   //