New Settings → General toggle `Use original filenames on download` (off by
default). When on, single-photo downloads, bulk/selection zips, and per-event
archive zips surface `photos.original_filename` instead of the sanitized
storage filename. Storage paths are unchanged.
- Content-Disposition uses RFC 5987 (`filename=` ASCII + `filename*=UTF-8''…`)
so unicode camera filenames survive while header-injection bytes are stripped.
- Zip entries are deduplicated with a deterministic `_1` / `_2` suffix on
collision (folder structure preserved in archive zips).
- Pre-generated download-all zips and the in-memory setting cache are
invalidated when the toggle flips so the next download rebuilds with the
new names.
- Falls back to the storage filename whenever `original_filename` is null
(legacy uploads predating migration 062).
Paul Nothaft
7eeef2ba98