Set the Wayland app_id to `pixelpass` so the compositor matches the
installed pixelpass.desktop and uses its Icon= in the titlebar/taskbar,
replacing the generic fallback. Also embed a 256px PNG (rendered from
assets/pixelpass.svg) and set it via with_icon for X11 _NET_WM_ICON, and
add StartupWMClass=pixelpass to the desktop entry for robust window↔entry
matching across desktop environments. No new deps — eframe already pulls
the image crate, and icon_data::from_png_bytes decodes the embed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
