New round corners and confirmation dialog

This update introduces a new round corners parameter for the Torus primitive and adds a confirmation dialog before closing files.

Changes

• New round corners parameter for Torus primitive.
• Added confirmation dialog before closing file to avoid data loss.
• Toolbar now shows the "+" menu.
• Fixed cloner behaviour when editing materials.
• Fixed transform controls/resize helper hover priority.
• Fixed issue of duplicated light sources on creation.
• Fixed blending mode select on windows.
• Several minor fixes.