Fix Kornia pad import compatibility

[omribz156]

Fixes #496.

Summary

• Removed the pad import from kornia.geometry.transform.pyramid.
• Reused the existing torch.nn.functional as F import for the two padding calls in pyramid_blending.py.

This keeps the local reflect padding behavior without depending on Kornia exporting pad from its pyramid module, which is what breaks on newer Kornia installs. It should also help the related Cannot import name 'pad' report in #494.

Verification

• python -m py_compile pyramid_blending.py
• git diff --check

I did not run a full ComfyUI/Kornia runtime smoke locally because this machine does not have torch installed.

This was implemented with Codex assistance, with the patch kept focused and reviewed before opening.