- Introduce `openExternal` IPC handler in `electron/main.ts` for opening external links via the default browser or native app.
- Update typings in `electron.d.ts` and `preload.ts` to include `openExternal`.
- Refactor `ComposerRightBar` and `LeftBar` components to leverage `electron.openExternal` for external link actions (e.g., Facebook, Discord).
- Add offline mode logic to filter navigation options in `ComposerRightBar` and `LeftBar`.
- Enhance footer bar to display book titles when chapters are unavailable.