MG-Link Trial publicfix + Rio app icon rebuild

Changes:
- Replaced macOS .app Finder/Dock icon with Mitsuki Rio face icon.
- Replaced Ren'Py game/gui/window_icon.png with Mitsuki Rio face icon.
- Added/updated PC icon.ico and window_icon.png.

Source image:
- /Users/yuyukuma/.hermes/workspace-silica/references/rio_reference_icon.png

Verification:
- unzip -tq: Mac/PC OK
- Mac app icon.icns: replaced
- Ren'Py game/gui/window_icon.png: replaced

SHA256:
5e55661e1d81d60b966a9003eabc082eee57019976af35d011c3f5ee8f5b5405  mg_link_mini_demo-1.0-mac.zip
4a7c92abe40ec7961a52db4a4354b7cff737a823989d96898d08efe81a7bca26  mg_link_mini_demo-1.0-pc.zip