Adds a third section to the Batch Upload page that attaches plate movies to
shots derived from the filename: DH2_VFX_058_120_REF.mov becomes the plate
"REF" on shot DH2_VFX_058_120. Shot matching reuses findMatchingShotCode, so
it behaves like the rest of the page (case-insensitive, longest code wins,
underscore-boundary only) and the filename remainder becomes the label.
Bytes go straight to Hetzner via the existing presign endpoint since plates
are multi-GB, with XHR for per-file progress. Files whose shot already has a
plate of the same name are skipped so re-running a batch does not stack
duplicates.
Also resets the thumbnail and plate previews when the project changes — they
are resolved against a specific project, but only the version-upload flow was
being cleared.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>