What's New: 3D File Preview Updates

Overview

Expanded 3D previews in the Library File Manager and Printer File Manager.
Added STL support (interactive 3D view) alongside existing 3MF/G-code previews.
Improved multi-plate handling for 3MF files in the printer file manager.

Library File Manager (Files Page)

3D preview now supports .3mf, .gcode, and .stl files.
STL files open in the same viewer modal used by 3MF files.
Plate-aware selection continues to work for 3MF files with multiple plates.

Printer File Manager (Printers → File Manager)

Added a 3D View action for .3mf, .gcode, and .stl files on the printer.
New printer-side 3MF plate endpoints:
- Plate list and metadata retrieval.
- Plate thumbnail retrieval.
Added a printer-side gcode preview endpoint for 3MF and .gcode files.
STL models are centered on the build sheet in the 3D viewer.

Model Viewer Enhancements

Added STL rendering support using STLLoader.
Viewer now selects the correct rendering pipeline based on file type.
STL models auto-center on the build plate for a consistent viewing experience.

Affected Areas

Frontend: File Manager modals and 3D viewer.
Backend: Printer file preview endpoints for plates, plate thumbnails, and gcode.