launcher: add Steam and Waydroid badges

[sickle-phin]

Description

This PR adds Steam and Waydroid badges to the launcher.
It uses system icons instead of images from the asset folder.

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes existing behavior)
• Refactor / internal cleanup
• Documentation
• Other

Related issues

Screenshots / video

Checklist

• My code follows the conventions in CONTRIBUTING.md
• I have tested my changes locally
• New user-facing strings are wrapped in I18n.tr() with translator context, reusing existing terms where possible
• Go changes: ran make fmt, added/updated tests, make test passes, and go mod tidy is clean
• QML changes: ran make lint-qml with no new warnings
• I have opened a corresponding pull request in dlx-docs to document any new behaviors: https://github.com/AvengeMedia/DankLinux-Docs

[Purian23]

Thanks for the PR! Couple of items here:

1. Blank badge visible only checks assetPath.length, so missing theme icons still show an empty slot. Hide when iconPath is empty (prefer iconPath(name, true) like DesktopService/Paths), or ship SVGs like the other sources.

2. Steam scope only matches steam steam://rungameid/ and loses to earlier flatpak/nix branches. Note native only or broader to Widen/reorder the heuristics.

Nice to have: Waydroid exec variants + a couple screenshots.