feat: add EndOfBookMenuActivity replacing static end-of-book text

Interactive menu shown when reaching the end of a book with options:
Archive Book, Delete Book, Back to Beginning, Close Book, Close Menu.
Wired into EpubReaderActivity, XtcReaderActivity, and TxtReaderActivity
(TXT shows menu when user tries to advance past the last page).

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

src/activities/reader/EndOfBookMenuActivity.cpp

@@ -0,0 +1,97 @@
+#include "EndOfBookMenuActivity.h"
+
+#include <GfxRenderer.h>
+#include <I18n.h>
+
+#include "MappedInputManager.h"
+#include "components/UITheme.h"
+#include "fontIds.h"
+
+void EndOfBookMenuActivity::buildMenuItems() {
+  menuItems.clear();
+  menuItems.push_back({Action::ARCHIVE, StrId::STR_ARCHIVE_BOOK});
+  menuItems.push_back({Action::DELETE, StrId::STR_DELETE_BOOK});
+  menuItems.push_back({Action::BACK_TO_BEGINNING, StrId::STR_BACK_TO_BEGINNING});
+  menuItems.push_back({Action::CLOSE_BOOK, StrId::STR_CLOSE_BOOK});
+  menuItems.push_back({Action::CLOSE_MENU, StrId::STR_CLOSE_MENU});
+}
+
+void EndOfBookMenuActivity::onEnter() {
+  Activity::onEnter();
+  selectedIndex = 0;
+  requestUpdate();
+}
+
+void EndOfBookMenuActivity::onExit() { Activity::onExit(); }
+
+void EndOfBookMenuActivity::loop() {
+  buttonNavigator.onNext([this] {
+    selectedIndex = ButtonNavigator::nextIndex(selectedIndex, static_cast<int>(menuItems.size()));
+    requestUpdate();
+  });
+
+  buttonNavigator.onPrevious([this] {
+    selectedIndex = ButtonNavigator::previousIndex(selectedIndex, static_cast<int>(menuItems.size()));
+    requestUpdate();
+  });
+
+  if (mappedInput.wasReleased(MappedInputManager::Button::Confirm)) {
+    if (selectedIndex < static_cast<int>(menuItems.size())) {
+      auto cb = onAction;
+      cb(menuItems[selectedIndex].action);
+      return;
+    }
+  }
+
+  if (mappedInput.wasReleased(MappedInputManager::Button::Back)) {
+    auto cb = onAction;
+    cb(Action::CLOSE_MENU);
+    return;
+  }
+}
+
+void EndOfBookMenuActivity::render(Activity::RenderLock&&) {
+  renderer.clearScreen();
+
+  const auto pageWidth = renderer.getScreenWidth();
+  const auto pageHeight = renderer.getScreenHeight();
+
+  constexpr int popupMargin = 20;
+  constexpr int lineHeight = 30;
+  constexpr int titleHeight = 40;
+  const int optionCount = static_cast<int>(menuItems.size());
+  const int popupH = titleHeight + popupMargin + lineHeight * optionCount + popupMargin;
+  const int popupW = pageWidth - 60;
+  const int popupX = (pageWidth - popupW) / 2;
+  const int popupY = (pageHeight - popupH) / 2;
+
+  // Popup border and background
+  renderer.fillRect(popupX - 2, popupY - 2, popupW + 4, popupH + 4, true);
+  renderer.fillRect(popupX, popupY, popupW, popupH, false);
+
+  // Title
+  renderer.drawText(UI_12_FONT_ID, popupX + popupMargin, popupY + 8, tr(STR_END_OF_BOOK), true, EpdFontFamily::BOLD);
+
+  // Divider line
+  const int dividerY = popupY + titleHeight;
+  renderer.fillRect(popupX + 4, dividerY, popupW - 8, 1, true);
+
+  // Menu items
+  const int startY = dividerY + popupMargin / 2;
+  for (int i = 0; i < optionCount; ++i) {
+    const int itemY = startY + i * lineHeight;
+    const bool isSelected = (i == selectedIndex);
+
+    if (isSelected) {
+      renderer.fillRect(popupX + 2, itemY, popupW - 4, lineHeight, true);
+    }
+
+    renderer.drawText(UI_10_FONT_ID, popupX + popupMargin, itemY, I18N.get(menuItems[i].labelId), !isSelected);
+  }
+
+  // Button hints
+  const auto labels = mappedInput.mapLabels(tr(STR_CLOSE_MENU), tr(STR_SELECT), tr(STR_DIR_UP), tr(STR_DIR_DOWN));
+  GUI.drawButtonHints(renderer, labels.btn1, labels.btn2, labels.btn3, labels.btn4);
+
+  renderer.displayBuffer();
+}