Two follow-ups on the same feature branch:
1. Bake EXIF orientation into generated thumbnails. The `image` crate
doesn't apply Orientation on load, and `save_with_format(..Jpeg)`
drops EXIF — so portrait phone shots ended up sideways in any client
that displays the cached thumb directly (no EXIF tag for the browser
to compensate from). New `exif::read_orientation` reads the tag
cheaply (no full EXIF parse) and `exif::apply_orientation` does the
rotate/flip via image's existing `rotate90/180/270` + `fliph/flipv`.
Applied in both branches of `generate_image_thumbnail` (RAW embedded-
JPEG path and the regular `image::open` path). Existing thumbnails
in the cache are still wrong-orientation; wipe the thumb dir or run
a one-off backfill once this lands.
2. Optional `library` query param on `/photos/exif`. Accepts numeric id
or name (same shape as `/image?library=...`), resolved via the
existing `resolve_library_param` helper so a bad value 400s before
we touch the DAO. Filter is applied post-query in the handler
rather than pushed into `query_by_exif` to keep the DAO trait
(and its test mocks) unchanged. Cheap enough at typical library
counts; can be moved into SQL later if it ever isn't.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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