* fix(app): adjust CSP settings for skin manager to work

* tweak: allow current Tauri scheme in CSP

* tweak: remove references to invalid `sunny.png` texture in skin models

These were causing load errors in production app builds.

* tweak: use proper URL imports for skin models

This fixes importing these models in production builds of the app.

* chore(app-frontend): use more proper import style for glTF assets

* tweak: use proper URL imports for skin models in more places