ci: fix AppImage build hanging by using portable appimage format

- Add appimage target back to tauri.conf.json
- Force reinstall tauri-cli from feat/truly-portable-appimage branch
- Add 10 minute timeout to prevent indefinite hangs
- Add logging to verify correct tauri-cli version is installed

This fixes the issue where AppImage builds would hang at 'Running input plugin: gtk' by using the new portable appimage format that bypasses linuxdeploy entirely.