UI: Apply transforms/crops correctly to sources on paste

Applies transformations correctly to copy/pasted sources when copy and
pasting multiple. Previously the transformation/crop state was stored in
a single variable on copy so it would only apply the transformations to
one of the selected sources on paste instead of what the state was when
copied.
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Gitea Version: 1.28.0+dev-477-g8b6ad49a5f