Importing basic Simple Geometry meshes from FunGT UI

[juanchuletas]

Summary

Implement mesh addition from UI to allow users select from basic geometries.

Description

Currently, FunGT requires users to specify simple geometries programmatically. Users need a intuitive way to load simple geometries directly from the GUI interface, similar to professional graphics tools.

Requirements

Core Functionality

• Simple add geometry Dialog: Native picker for common 3D formats

User Experience Goals

• One-click workflow: Mesh → Add → Simple Geometry

Acceptance Criteria

• User can open file dialog from GUI
• Appearing geometries
• Deleting geometries