Fix GUI visualization and parameter controls

[uttkxrrsh]

Summary

• make the 2D garment pattern fill its visualization panel so it remains visible
• add manual numeric inputs alongside sliders while preserving out-of-range typed values
• allow negative back-collar depth values down to -0.2
• keep manual inputs synchronized and enabled/disabled with their sliders
• support inline SVG icons with current NiceGUI sanitization behavior

Validation

• python -m py_compile gui/callbacks.py
• parsed both modified YAML design-parameter files successfully
• verified the branch changes only the two design-parameter files and gui/callbacks.py