fix(metadata): recall z_image_shift correctly (#9139)

* fix(metadata): recall z_image_shift correctly

Widen the validator range to match the param's actual max (10) so saved
shift values above 3 are recalled, and handle absent/null values by
recalling as auto (null) when the recalled image is a Z-Image.

* fix(metadata): always emit z_image_shift, render auto in viewer

The backend's CoreMetadataInvocation uses model_dump(exclude_none=True),
so passing null/undefined for z_image_shift drops the field from the
saved metadata entirely. As a result, an image generated with auto
shift had no shift entry in its metadata viewer.

Write the literal 'auto' as a sentinel when shift is null so the field
survives serialization, and teach the parser to map it back to null on
recall. Also wire the ZImageShift handler into the Recall Parameters
tab (it was defined but never rendered).