feat: add BookManageMenuActivity popup sub-activity

Contextual popup menu for book management with Archive/Unarchive,
Delete, Delete Cache Only, and Reindex options. Supports long-press
on Reindex to trigger full reindex including cover/thumbnail regen.

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

src/activities/home/BookManageMenuActivity.h

@@ -0,0 +1,59 @@
+#pragma once
+
+#include <I18n.h>
+
+#include <functional>
+#include <string>
+#include <vector>
+
+#include "../Activity.h"
+#include "util/ButtonNavigator.h"
+
+class BookManageMenuActivity final : public Activity {
+ public:
+  enum class Action {
+    ARCHIVE,
+    UNARCHIVE,
+    DELETE,
+    DELETE_CACHE,
+    REINDEX,
+    REINDEX_FULL,
+  };
+
+  explicit BookManageMenuActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
+                                  const std::string& bookPath, bool isArchived,
+                                  const std::function<void(Action)>& onAction,
+                                  const std::function<void()>& onCancel)
+      : Activity("BookManageMenu", renderer, mappedInput),
+        bookPath(bookPath),
+        archived(isArchived),
+        onAction(onAction),
+        onCancel(onCancel) {
+    buildMenuItems();
+  }
+
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+  void render(Activity::RenderLock&&) override;
+
+ private:
+  struct MenuItem {
+    Action action;
+    StrId labelId;
+  };
+
+  std::string bookPath;
+  bool archived;
+  std::vector<MenuItem> menuItems;
+  int selectedIndex = 0;
+  ButtonNavigator buttonNavigator;
+
+  bool ignoreNextConfirmRelease = false;
+  static constexpr unsigned long LONG_PRESS_MS = 700;
+
+  const std::function<void(Action)> onAction;
+  const std::function<void()> onCancel;
+
+  void buildMenuItems();
+};