Dates the images and videos stored before capture dates existed (V200).

New uploads get their date from ProcessFileJob. Files already stored have none, so this job walks them in @batch_size batches, in uuid order, reads each one's bytes and records a date through the same CaptureDate.replace?/2 guard. Every visited file ends up with a date: when its bytes cannot be read, the file name or the upload time is used.

Chaining. Each run handles one batch and enqueues the next with a cursor ("after", the last uuid it visited), so a file is visited once per pass even when it cannot be dated — a stuck row cannot loop the chain. Only one pending run exists at a time (unique over [:worker, :queue], ignoring the cursor); a run that is executing does not count, so it can enqueue its own successor.

An edited image is dated from its unedited backup (original_file_uuid) when it has one: an edit keeps only the ICC profile, so the edited bytes carry no EXIF.

Start a pass in the background with enqueue/0, or run one to completion in the calling process with run_pass/1 — which is what mix phoenix_kit.storage.backfill_capture_dates does.