fix: add txt books to recent tab (#526)

Cherry-picked from upstream PR #526
Resolved conflict: kept local cover generation code

src/activities/reader/TxtReaderActivity.cpp

@@ -11,6 +11,7 @@
 #include "CrossPointSettings.h"
 #include "CrossPointState.h"
 #include "MappedInputManager.h"
+#include "RecentBooksStore.h"
 #include "ScreenComponents.h"
 #include "fontIds.h"
 
@@ -103,11 +104,12 @@ void TxtReaderActivity::onEnter() {
     });
   }
 
-  // Save current txt as last opened file and cache title for home screen
+  // Save current txt as last opened file and add to recent books
   APP_STATE.openEpubPath = txt->getPath();
   APP_STATE.openBookTitle = txt->getTitle();
   APP_STATE.openBookAuthor.clear();  // TXT files don't have author metadata
   APP_STATE.saveToFile();
+  RECENT_BOOKS.addBook(txt->getPath());
 
   // Trigger first update
   updateRequired = true;