Fill Tool (Bucket)

[pexeixv]

Goal:
Implement a fill tool to fill connected areas with a single color.

Requirements:

• Click a cell to fill all adjacent same-colored cells with the selected color.
• Must work with Undo/Redo.

Notes:
Enables fast coloring of large uniform areas.

[palakag29]

@pexeixv @ctrl-7 please assign this issue to me