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/KOReaderSyncActivity.cpp

@@ -50,6 +50,12 @@ void wifiOff() {
 }
 }  // namespace
 
+void KOReaderSyncActivity::deferFinish(bool success) {
+  RenderLock lock(*this);
+  pendingFinishSuccess = success;
+  pendingFinish = true;
+}
+
 void KOReaderSyncActivity::onWifiSelectionComplete(const bool success) {
   if (!success) {
     LOG_DBG("KOSync", "WiFi connection failed, exiting");
@@ -89,6 +95,10 @@ void KOReaderSyncActivity::performSync() {
     documentHash = KOReaderDocumentId::calculate(epubPath);
   }
   if (documentHash.empty()) {
+    if (syncMode == SyncMode::PUSH_ONLY) {
+      deferFinish(false);
+      return;
+    }
     {
       RenderLock lock(*this);
       state = SYNC_FAILED;
@@ -106,11 +116,16 @@ void KOReaderSyncActivity::performSync() {
   }
   requestUpdateAndWait();
 
+  if (syncMode == SyncMode::PUSH_ONLY) {
+    // Skip fetching remote progress entirely -- just upload local position
+    performUpload();
+    return;
+  }
+
   // Fetch remote progress
   const auto result = KOReaderSyncClient::getProgress(documentHash, remoteProgress);
 
   if (result == KOReaderSyncClient::NOT_FOUND) {
-    // No remote progress - offer to upload
     {
       RenderLock lock(*this);
       state = NO_REMOTE_PROGRESS;
@@ -174,6 +189,11 @@ void KOReaderSyncActivity::performUpload() {
 
   if (result != KOReaderSyncClient::OK) {
     wifiOff();
+    if (syncMode == SyncMode::PUSH_ONLY) {
+      LOG_DBG("KOSync", "PUSH_ONLY upload failed: %s", KOReaderSyncClient::errorString(result));
+      deferFinish(false);
+      return;
+    }
     {
       RenderLock lock(*this);
       state = SYNC_FAILED;
@@ -184,6 +204,11 @@ void KOReaderSyncActivity::performUpload() {
   }
 
   wifiOff();
+  if (syncMode == SyncMode::PUSH_ONLY) {
+    LOG_DBG("KOSync", "PUSH_ONLY upload succeeded");
+    deferFinish(true);
+    return;
+  }
   {
     RenderLock lock(*this);
     state = UPLOAD_COMPLETE;
@@ -196,6 +221,11 @@ void KOReaderSyncActivity::onEnter() {
 
   // Check for credentials first
   if (!KOREADER_STORE.hasCredentials()) {
+    if (syncMode == SyncMode::PUSH_ONLY) {
+      LOG_DBG("KOSync", "PUSH_ONLY: no credentials, finishing silently");
+      deferFinish(false);
+      return;
+    }
     state = NO_CREDENTIALS;
     requestUpdate();
     return;
@@ -335,6 +365,15 @@ void KOReaderSyncActivity::render(RenderLock&&) {
 }
 
 void KOReaderSyncActivity::loop() {
+  if (pendingFinish) {
+    pendingFinish = false;
+    ActivityResult result;
+    result.isCancelled = !pendingFinishSuccess;
+    setResult(std::move(result));
+    finish();
+    return;
+  }
+
   if (state == NO_CREDENTIALS || state == SYNC_FAILED || state == UPLOAD_COMPLETE) {
     if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
       ActivityResult result;