fix: placeholder cover text, indexing timing, TOC long-press, cache deletion UI

- Fix fp4 fixed-point misuse in PlaceholderCoverGenerator (advanceX is 12.4
  fixed-point, not pixels) causing only first letter of each word to render
- Remove duplicate silentIndexNextChapterIfNeeded() call from loop() that
  blocked UI before render, preventing the indexing indicator from showing
- Fix indexing icon Y position to align within the status bar
- Add ignoreNextConfirmRelease to EpubReaderChapterSelectionActivity so
  long-press confirm release doesn't immediately select the first TOC item
- Reload recent books after cache deletion in HomeActivity and clear stale
  ignoreNextConfirmRelease flag to fix "no open books" and double-press bugs

Made-with: Cursor

src/activities/reader/EpubReaderChapterSelectionActivity.cpp

@@ -48,6 +48,10 @@ void EpubReaderChapterSelectionActivity::loop() {
   const int totalItems = getTotalItems();
 
   if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
+    if (ignoreNextConfirmRelease) {
+      ignoreNextConfirmRelease = false;
+      return;
+    }
     const auto newSpineIndex = epub->getSpineIndexForTocIndex(selectorIndex);
     if (newSpineIndex == -1) {
       ActivityResult result;