Add Defi app icon assets

[qeude]

Summary

• Add the Defi Icon Composer package and window artwork.
• Add light and dark icon previews to the README.
• Center the project title and CI badge around the new branding.

Testing

• Not run (asset and documentation-only change).

[greptile-apps]

Greptile Summary

The PR adds Defi’s Icon Composer artwork, README previews, and icon compilation to local application and DMG packaging flows.

• Adds the Icon Composer package and source SVG.
• Compiles icon resources and adds generated icon metadata to staged application bundles.
• Adds light and dark branding previews to the README.

Confidence Score: 5/5

The PR appears safe to merge because no blocking failure remains established on the current head.

No blocking failure remains.

Important Files Changed

Filename	Overview
Support/Defi.icon/icon.json	Defines the layered light and dark Icon Composer artwork used by the application bundle.
script/build_and_run.sh	Compiles the icon package into application resources and inserts generated icon metadata before signing.
script/package_dmg.sh	Adds the same icon compilation and metadata integration to release DMG packaging.
README.md	Centers the project branding and adds theme-aware icon previews.

_{Reviews (2): Last reviewed commit: "feat(icon): add branded app icon to buil..." | Re-trigger Greptile}