Feature: Add offset functionality to Designer

[giro-dev]

This PR adds a new offset feature to the Designer module. The offset functionality allows users to create inward or outward offsets from selected shapes, which is particularly useful for creating toolpath offsets, creating shape outlines, or generating insets for shapes.

Features

• Create offsets from any selected shape or group of shapes
• Offset direction options: inward, outward, or both
• Configurable join styles (round, bevel, mitre) for offset corners
• Boolean operation option to union all resulting shapes
• Live preview of the offset result
• Support for complex shapes and groups

Implementation details

• Uses JTS Topology Suite for geometric operations
• Handles various shape types through a unified interface
• Maintains the original selection after applying offsets
• Provides fallback handling for complex geometries that might cause errors

Usage

1. Select one or more shapes in the Designer
2. Open the Offset dialog from the menu
3. Configure the offset distance, direction, and join style
4. Toggle the "Union all" option if desired
5. Click OK to apply the offset

The offset feature works with all cuttable entities and preserves the original selection, making it easy to continue working with both the original and offset shapes.

[giro-dev]

I've used this icon I've found but not sure if you are using a certain icon collection that cold have more coherence with the application look.

[breiler]

This could be replaced with a com.willwinder.universalgcodesender.uielements.components.UnitSpinner at a later time

[breiler]

I think you should take credit here =)

[giro-dev]

its my first time collaborating to an opensource project xd
thanks to point it, I'll take care in following PRs ;)

[breiler]

Regarding the icons, I have started using Phosphor icons as they are easy to work with:
https://phosphoricons.com/?weight=fill

I try to use one color for the original since this makes it easy to convert for dark themes using the script: scripts/svg_to_icons.sh

Don't worry about that now, I think it is good enough.