fix(installer): support TUXEDO OS and silence KDE Plasma 6 qtpaths noise

[charlypa]

• Resolve derivative distros to their base family via ID_LIKE (with a package-manager fallback) so TUXEDO OS (ID=tuxedo), Pop!_OS, Zorin, elementary, etc. install instead of failing 'Unsupported distribution'.
• In set_default_application, drop the dead qtpaths PATH-munging block and filter the cosmetic 'qtpaths: not found' stderr that xdg-mime emits on Qt6-only KDE systems (TUXEDO OS, Ubuntu 24.04 KDE). The default is still set via xdg-mime's generic backend; only the noise is removed.

Applied identically to installer.sh and installer-latest-experimental-build.sh.

What kind of change does this PR introduce?

• Bugfix - fixes issues- give issue github url/details here.
• Feature
• Docs
• Code style update
• Refactor
• Build-related changes
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Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

Tests done

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Checklist

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Other information

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[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud