feat(versions): schema and VersionDao for hash-keyed photo versions

photo_versions links a version's content_hash to its primary original's;
photo_version_references keeps provenance-only reference photos;
photo_version_display holds the global display choice. VersionDao covers
linking (chains flatten to the root), the display choice, per-original
summaries for /photos, the hidden-row set for non-SQL listings, and the
copy of the original's date/GPS/camera onto version rows. Also the SQL
predicate listings use to hide a version while its original is reachable.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

migrations/2026-10-30-000000_add_photo_versions/down.sql

@@ -0,0 +1,3 @@
+DROP TABLE IF EXISTS photo_version_display;
+DROP TABLE IF EXISTS photo_version_references;
+DROP TABLE IF EXISTS photo_versions;