Normalize Wallpaper Engine project metadata and surface type in the UI

[louzt]

Issue Draft: Normalize Wallpaper Engine project metadata and surface type in the UI

Summary

Waypaper currently treats Wallpaper Engine entries mostly as preview files, which hides the real project type and makes scene, video, and web entries look like generic static wallpapers in the grid.

Repro

1. Point Waypaper at a Wallpaper Engine workshop directory.
2. Open entries such as:
   • 1470208181 (video)
   • 1768540735 (scene)
   • 1184182304 (web)
3. Compare what the UI shows with the corresponding project.json values.

Actual behavior

• The UI primarily reflects preview files.
• Users cannot reliably tell whether an entry is scene, video, or web.
• This leads to wrong expectations, especially for web wallpapers that legitimately use static previews.

Expected behavior

• Parse project.json consistently.
• Normalize the detected type to scene, video, web, or unknown.
• Show the detected type directly in the UI list/grid.
• Keep metadata normalized so later routing logic can use it.

Notes

• This is an independent UI/data-model fix.
• It should land before any backend handoff logic.

Validation

• Verify visible labels for at least one scene, one video, and one web Wallpaper Engine project.
• Confirm no regression for normal image folders.

Proposed branch

• fix/wallpaperengine-project-metadata