Fix(UI): Removed canvas' blur filter clipping by expanding image bounds

[DustyShoe]

Summary

This PR improves Blur filter behavior by adding padding to applied filter. It removes sharp edges caused by clipping with image/layer bounds if blur value is greater than 4.

Related Issues / Discussions

QA Instructions

• Extract a region of raster layer or pant a stroke on the empty layer.
• By accessing filter menu create and apply blur with value 8 or greater.
• Verify there's no rectangular sharp edges on blurred image.
• Verify there's no image shifting upon applying the filter.

Merge Plan

Should be safe to merge. The changes are scoped to the canvas filter path and only affect blur behavior: padding is applied in the blur graph and placement/bbox handling is stabilized. Other filters keep the existing flow. The only notable change is the new optional usePixelBbox on image objects, but it defaults to current behavior unless explicitly set (only blur uses it).

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)

[lstein]

@Pfannkuchensack Could you take on primary reviewer role for this one?