Pretty sure it works but kosync is down right now even on my other devices

src/activities/reader/KOReaderSyncActivity.h

@@ -0,0 +1,95 @@
+#pragma once
+#include <Epub.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/semphr.h>
+#include <freertos/task.h>
+
+#include <functional>
+#include <memory>
+
+#include "KOReaderSyncClient.h"
+#include "ProgressMapper.h"
+#include "activities/ActivityWithSubactivity.h"
+
+/**
+ * Activity for syncing reading progress with KOReader sync server.
+ *
+ * Flow:
+ * 1. Connect to WiFi (if not connected)
+ * 2. Calculate document hash
+ * 3. Fetch remote progress
+ * 4. Show comparison and options (Apply/Upload/Cancel)
+ * 5. Apply or upload progress
+ */
+class KOReaderSyncActivity final : public ActivityWithSubactivity {
+ public:
+  using OnCancelCallback = std::function<void()>;
+  using OnSyncCompleteCallback = std::function<void(int newSpineIndex, int newPageNumber)>;
+
+  explicit KOReaderSyncActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
+                                const std::shared_ptr<Epub>& epub, const std::string& epubPath, int currentSpineIndex,
+                                int currentPage, int totalPagesInSpine, OnCancelCallback onCancel,
+                                OnSyncCompleteCallback onSyncComplete)
+      : ActivityWithSubactivity("KOReaderSync", renderer, mappedInput),
+        epub(epub),
+        epubPath(epubPath),
+        currentSpineIndex(currentSpineIndex),
+        currentPage(currentPage),
+        totalPagesInSpine(totalPagesInSpine),
+        onCancel(std::move(onCancel)),
+        onSyncComplete(std::move(onSyncComplete)) {}
+
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+  bool preventAutoSleep() override { return state == CONNECTING || state == SYNCING; }
+
+ private:
+  enum State {
+    WIFI_SELECTION,
+    CONNECTING,
+    SYNCING,
+    SHOWING_RESULT,
+    UPLOADING,
+    UPLOAD_COMPLETE,
+    NO_REMOTE_PROGRESS,
+    SYNC_FAILED,
+    NO_CREDENTIALS
+  };
+
+  std::shared_ptr<Epub> epub;
+  std::string epubPath;
+  int currentSpineIndex;
+  int currentPage;
+  int totalPagesInSpine;
+
+  TaskHandle_t displayTaskHandle = nullptr;
+  SemaphoreHandle_t renderingMutex = nullptr;
+  bool updateRequired = false;
+
+  State state = WIFI_SELECTION;
+  std::string statusMessage;
+  std::string documentHash;
+
+  // Remote progress data
+  bool hasRemoteProgress = false;
+  KOReaderProgress remoteProgress;
+  CrossPointPosition remotePosition;
+
+  // Local progress as KOReader format (for display)
+  KOReaderPosition localProgress;
+
+  // Selection in result screen (0=Apply, 1=Upload, 2=Cancel)
+  int selectedOption = 0;
+
+  OnCancelCallback onCancel;
+  OnSyncCompleteCallback onSyncComplete;
+
+  void onWifiSelectionComplete(bool success);
+  void performSync();
+  void performUpload();
+
+  static void taskTrampoline(void* param);
+  [[noreturn]] void displayTaskLoop();
+  void render();
+};