Adds a fullscreen image preview dialog to the model info panel with
navigation, copy-prompt support, generation metadata display, and
referenced resources listing.
Extends CivitAI backend extraction to handle varied metadata key names
(negativePrompt, Clip skip, Model, etc.) and surfaces clip_skip, width,
height, tags, resources, and raw metadata through the new preview UI.
Renames z-index variable to reserve a dedicated layer for the preview
backdrop.