After testing out the icon on device for a bit, we decided the osu! logo
was a little too large.
This PR replaces the app icons with a new version where the sizing of
the logo itself is aligned to Apple's recommended boundary.
<img width="198" height="169" alt="Screenshot 2026-01-30 at 2 33 24 PM"
src="https://github.com/user-attachments/assets/c66fb016-9c19-4ff5-814a-6f302ec459ca"
/>
Removes the previous `AppIcon.appiconset` bundle and replaces it with
all of the necessary asset slices to enable all of the Liquid Glass
variants of the app icon on iOS 26, while also preserving backwards
compatibility with older iOS versions.
<img width="1164" height="388" alt="LiquidGlass"
src="https://github.com/user-attachments/assets/7d6e7a90-3fe5-4853-9c63-35144359f49e"
/>
---------
Co-authored-by: Dean Herbert <pe@ppy.sh>