Three fixes for BitFun logo not displaying correctly on Linux:

1. SplashScreen opacity: increase idle animation from 38% to 85%
   - Logo was nearly invisible on dark background with only 38% opacity

2. Replace Logo-ICON.png with icon.png for in-app logo
   - Previous Logo-ICON.png had 46% fully transparent pixels
   - icon.png has only 2.7% transparent pixels, much more visible

3. Add multi-size icons for Linux desktop integration
   - Tauri only installed 1024x1024 icon, causing taskbar/dock issues
   - Added 16x16 through 512x512 icons for proper GNOME/flatpak support
   - Updated tauri.conf.json deb.files to include all icon sizes
   - Added post-install script to update icon cache

Generated with BitFun
Co-Authored-By: BitFun