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.h

@@ -1,8 +1,5 @@
 #pragma once
 #include <EpdFontFamily.h>
-#include <freertos/FreeRTOS.h>
-#include <freertos/semphr.h>
-#include <freertos/task.h>
 
 #include <functional>
 #include <string>
@@ -27,6 +24,7 @@ class DictionaryDefinitionActivity final : public Activity {
   void onEnter() override;
   void onExit() override;
   void loop() override;
+  void render(Activity::RenderLock&&) override;
 
  private:
   // A positioned text segment within a wrapped line (pre-calculated x offset and style).
@@ -61,17 +59,10 @@ class DictionaryDefinitionActivity final : public Activity {
   int currentPage = 0;
   int linesPerPage = 0;
   int totalPages = 0;
-  bool updateRequired = false;
   bool firstRender = true;
 
-  TaskHandle_t displayTaskHandle = nullptr;
-  SemaphoreHandle_t renderingMutex = nullptr;
-
   std::vector<TextAtom> parseHtml(const std::string& html);
   static std::string decodeEntity(const std::string& entity);
   static bool isRenderableCodepoint(uint32_t cp);
   void wrapText();
-  void renderScreen();
-  static void taskTrampoline(void* param);
-  [[noreturn]] void displayTaskLoop();
 };