[Docs]: Improve GIF transparency in README for GitHub light mode

[majockbim]

The README GIF currently looks great in GitHub dark mode, but in light mode there are visible black artifacts/spots around parts of the animation. These appear to be pixels that were not fully converted to transparency when the GIF was processed.

The GIF was made transparent using ffmpeg, so this may require revisiting the transparency/color keying step or exporting with a cleaner alpha/transparency workflow.

Acceptance Criteria

• README GIF displays cleanly in GitHub dark mode
• README GIF displays cleanly in GitHub light mode
• No visible black spots/artifacts remain around the animated subject
• Updated GIF is committed in place of the current one
• README preview is checked against both GitHub themes

Notes

This is mostly a visual polish issue, but it affects how professional the README feels for users browsing in light mode.