Refs #330
## Summary
- add standard Linux hicolor icon sizes to the Tauri package outputs
- enable the GTK app id on Linux and ship a matching reverse-DNS desktop
entry alias for shell association
- mark the alias desktop entry `NoDisplay=true` so it does not surface
as a duplicate launcher in desktop menus
- include the same alias desktop entry for AppImage so the fix is not
limited to deb/rpm packages
## Validation
- confirmed in the Linux VM that the desktop-integrated launch no longer
shows the generic taskbar icon
- verified the alias desktop entry is now hidden from app menus via
`NoDisplay=true`
- attempted a fresh `tauri build --bundles deb`; the build still hits
the known optional `@tauri-apps/cli` native-binding issue in this
workspace after prebuild, not a code/config error from this PR
1b829094ef