mod: restore missing mod features from resync audit

Re-add KOReaderSyncActivity PUSH_ONLY mode (PR #1090):
- SyncMode enum with INTERACTIVE/PUSH_ONLY, deferFinish pattern
- Push & Sleep menu action in EpubReaderMenuActivity
- ActivityManager::requestSleep() for activity-initiated sleep
- main.cpp checks isSleepRequested() each loop iteration

Wire EndOfBookMenuActivity into EpubReaderActivity:
- pendingEndOfBookMenu deferred flag avoids render-lock deadlock
- Handles all 6 actions: ARCHIVE, DELETE, TABLE_OF_CONTENTS,
  BACK_TO_BEGINNING, CLOSE_BOOK, CLOSE_MENU

Add book management to reader menu:
- ARCHIVE_BOOK, DELETE_BOOK, REINDEX_BOOK actions with handlers

Port silent next-chapter pre-indexing:
- silentIndexNextChapterIfNeeded() proactively indexes next chapter
  when user is near end of current one, eliminating load screens

Add per-book letterbox fill toggle in reader menu:
- LETTERBOX_FILL cycles Default/Dithered/Solid/None
- Loads/saves per-book override via BookSettings
- bookCachePath constructor param added to EpubReaderMenuActivity

Made-with: Cursor

src/activities/reader/EpubReaderMenuActivity.cpp

@@ -11,7 +11,8 @@
 EpubReaderMenuActivity::EpubReaderMenuActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
                                                const std::string& title, const int currentPage, const int totalPages,
                                                const int bookProgressPercent, const uint8_t currentOrientation,
-                                               const bool hasFootnotes, bool isBookmarked, uint8_t currentFontSize)
+                                               const bool hasFootnotes, bool isBookmarked, uint8_t currentFontSize,
+                                               const std::string& bookCachePath)
     : Activity("EpubReaderMenu", renderer, mappedInput),
       menuItems(buildMenuItems(hasFootnotes, isBookmarked)),
       title(title),
@@ -19,12 +20,18 @@ EpubReaderMenuActivity::EpubReaderMenuActivity(GfxRenderer& renderer, MappedInpu
       pendingFontSize(currentFontSize < CrossPointSettings::FONT_SIZE_COUNT ? currentFontSize : 0),
       currentPage(currentPage),
       totalPages(totalPages),
-      bookProgressPercent(bookProgressPercent) {}
+      bookProgressPercent(bookProgressPercent),
+      bookCachePath(bookCachePath) {
+  if (!bookCachePath.empty()) {
+    auto bookSettings = BookSettings::load(bookCachePath);
+    pendingLetterboxFill = bookSettings.letterboxFillOverride;
+  }
+}
 
 std::vector<EpubReaderMenuActivity::MenuItem> EpubReaderMenuActivity::buildMenuItems(bool hasFootnotes,
                                                                                      bool isBookmarked) {
   std::vector<MenuItem> items;
-  items.reserve(13);
+  items.reserve(16);
   // Mod menu order
   if (isBookmarked) {
     items.push_back({MenuAction::REMOVE_BOOKMARK, StrId::STR_REMOVE_BOOKMARK});
@@ -38,8 +45,13 @@ std::vector<EpubReaderMenuActivity::MenuItem> EpubReaderMenuActivity::buildMenuI
   items.push_back({MenuAction::GO_TO_PERCENT, StrId::STR_GO_TO_PERCENT});
   items.push_back({MenuAction::TOGGLE_ORIENTATION, StrId::STR_TOGGLE_ORIENTATION});
   items.push_back({MenuAction::TOGGLE_FONT_SIZE, StrId::STR_TOGGLE_FONT_SIZE});
+  items.push_back({MenuAction::LETTERBOX_FILL, StrId::STR_OVERRIDE_LETTERBOX_FILL});
   items.push_back({MenuAction::SYNC, StrId::STR_SYNC_PROGRESS});
+  items.push_back({MenuAction::PUSH_AND_SLEEP, StrId::STR_PUSH_AND_SLEEP});
   items.push_back({MenuAction::CLOSE_BOOK, StrId::STR_CLOSE_BOOK});
+  items.push_back({MenuAction::ARCHIVE_BOOK, StrId::STR_ARCHIVE_BOOK});
+  items.push_back({MenuAction::DELETE_BOOK, StrId::STR_DELETE_BOOK});
+  items.push_back({MenuAction::REINDEX_BOOK, StrId::STR_REINDEX_BOOK});
   items.push_back({MenuAction::DELETE_CACHE, StrId::STR_DELETE_CACHE});
   items.push_back({MenuAction::DELETE_DICT_CACHE, StrId::STR_DELETE_DICT_CACHE});
   return items;
@@ -81,6 +93,14 @@ void EpubReaderMenuActivity::loop() {
       return;
     }
 
+    if (selectedAction == MenuAction::LETTERBOX_FILL) {
+      int idx = (letterboxFillToIndex() + 1) % LETTERBOX_FILL_OPTION_COUNT;
+      pendingLetterboxFill = indexToLetterboxFill(idx);
+      if (!bookCachePath.empty()) saveLetterboxFill();
+      requestUpdate();
+      return;
+    }
+
     setResult(MenuResult{static_cast<int>(selectedAction), pendingOrientation, selectedPageTurnOption, pendingFontSize});
     finish();
     return;
@@ -155,6 +175,12 @@ void EpubReaderMenuActivity::render(RenderLock&&) {
       const auto width = renderer.getTextWidth(UI_10_FONT_ID, value);
       renderer.drawText(UI_10_FONT_ID, contentX + contentWidth - 20 - width, displayY, value, !isSelected);
     }
+
+    if (menuItems[i].action == MenuAction::LETTERBOX_FILL) {
+      const char* value = I18N.get(letterboxFillLabels[letterboxFillToIndex()]);
+      const auto width = renderer.getTextWidth(UI_10_FONT_ID, value);
+      renderer.drawText(UI_10_FONT_ID, contentX + contentWidth - 20 - width, displayY, value, !isSelected);
+    }
   }
 
   // Footer / Hints