mod: adapt mod activities to #774 render() pattern

Migrate 5 mod Activity subclasses from old polling-based
display task pattern to the upstream render() super-class
pattern with freeRTOS notification:

- EpubReaderBookmarkSelectionActivity
- DictionaryWordSelectActivity
- DictionarySuggestionsActivity
- DictionaryDefinitionActivity
- LookedUpWordsActivity

Changes: remove own TaskHandle/SemaphoreHandle/updateRequired,
use requestUpdate() + render(RenderLock&&) override, fix
potential deadlocks around enterNewActivity() calls.

Also fix stale conflict marker in EpubReaderMenuActivity.h.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/activities/reader/DictionaryDefinitionActivity.cpp

@@ -11,40 +11,14 @@
 #include "components/UITheme.h"
 #include "fontIds.h"
 
-void DictionaryDefinitionActivity::taskTrampoline(void* param) {
-  auto* self = static_cast<DictionaryDefinitionActivity*>(param);
-  self->displayTaskLoop();
-}
-
-void DictionaryDefinitionActivity::displayTaskLoop() {
-  while (true) {
-    if (updateRequired) {
-      updateRequired = false;
-      xSemaphoreTake(renderingMutex, portMAX_DELAY);
-      renderScreen();
-      xSemaphoreGive(renderingMutex);
-    }
-    vTaskDelay(10 / portTICK_PERIOD_MS);
-  }
-}
-
 void DictionaryDefinitionActivity::onEnter() {
   Activity::onEnter();
-  renderingMutex = xSemaphoreCreateMutex();
   wrapText();
-  updateRequired = true;
-  xTaskCreate(&DictionaryDefinitionActivity::taskTrampoline, "DictDefTask", 4096, this, 1, &displayTaskHandle);
+  requestUpdate();
 }
 
 void DictionaryDefinitionActivity::onExit() {
   Activity::onExit();
-  xSemaphoreTake(renderingMutex, portMAX_DELAY);
-  if (displayTaskHandle) {
-    vTaskDelete(displayTaskHandle);
-    displayTaskHandle = nullptr;
-  }
-  vSemaphoreDelete(renderingMutex);
-  renderingMutex = nullptr;
 }
 
 // ---------------------------------------------------------------------------
@@ -442,12 +416,12 @@ void DictionaryDefinitionActivity::loop() {
 
   if (prevPage && currentPage > 0) {
     currentPage--;
-    updateRequired = true;
+    requestUpdate();
   }
 
   if (nextPage && currentPage < totalPages - 1) {
     currentPage++;
-    updateRequired = true;
+    requestUpdate();
   }
 
   if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
@@ -465,7 +439,7 @@ void DictionaryDefinitionActivity::loop() {
   }
 }
 
-void DictionaryDefinitionActivity::renderScreen() {
+void DictionaryDefinitionActivity::render(Activity::RenderLock&&) {
   renderer.clearScreen();
 
   const bool landscape = orientation == CrossPointSettings::ORIENTATION::LANDSCAPE_CW ||