Replace Tauri with native UI

[antangelo]

We currently ship xdvdfs-web in the desktop app via Tauri, but this introduces a number of complexities:

• Tauri is still heavy to run in contrast to native tools
• It requires many dependencies, and requires local environment dependencies that make building xdvdfs more difficult
• It doesn't integrate with the main CI pipelines, and the desktop pipelines take significantly longer to run than the others
• There are platform-specific webkit bugs with WASM that cannot be worked around or controlled for

The pros of using Tauri are UI code sharing with xdvdfs-web, and having multi-platform support for free. In spite of these, the desktop platform is likely better served with a native UI that is not bound by the limitations of the filesystem access API.

xdvdfs-web should remain backend-agnostic with respect to how it accesses the filesystem, but the Tauri wrappers should be removed as part of this work.