feat(application): PSD layer separation and image quality/count threading

Convert GPT Image 2 layered PSD output into canvas image/text nodes with a
local separation fallback (new layer_separation.go, oov/psd dependency),
default layer-separation/edit-elements output_format to psd, and thread
imageQuality/imageCount through project generation and job processing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/go.sum

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