Add basic 2D touch-up tools above the preview

Kromacut could benefit from a small set of 2D editing tools for quick image touch-ups before moving into the 3D workflow.

The goal is not to become a full image editor, but to let users fix small details without leaving the app. For example, they may want to clean up stray pixels, fill gaps, remove tiny artifacts, draw simple corrections, or add text before generating the layered model.

The tools should live in the existing tool area above the 2D preview, alongside actions like crop, so they feel like part of the image-prep workflow rather than a separate mode.

Useful initial tools could include:

• Pencil/brush for simple drawing.
• Eraser or remove tool for small cleanup.
• Fill/bucket tool for replacing small areas.
• Text tool for adding labels or simple lettering.
• Color picker or palette-aware color selection.
• Undo/redo for edits.

A simple first version could start with only brush/eraser/text and expand later.

Desired outcome:
Users can make small visual edits inside Kromacut before generating the 3D model, especially when the original image has artifacts, missing details, or needs simple text/markings added.

Start by inspecting the existing tool area above the 2D preview, including the crop action, and trace how image-preparation changes feed the 3D workflow. Define a focused first tool set from the requested options and establish what edit history and completion behavior are required. Done means users can make small touch-ups inside Kromacut before generating the layered model.