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>

src/database/mod.rs

@@ -54,6 +54,7 @@ pub mod reconcile;
 pub mod schema;
 pub mod search_dao;
 pub mod user_ai_prefs_dao;
+pub mod version_dao;
 
 pub use calendar_dao::{CalendarEventDao, SqliteCalendarEventDao};
 pub use daily_summary_dao::{DailySummaryDao, InsertDailySummary, SqliteDailySummaryDao};
@@ -71,6 +72,7 @@ pub use precomputed_reel_dao::{PrecomputedReelDao, SqlitePrecomputedReelDao};
 pub use preview_dao::{PreviewDao, SqlitePreviewDao};
 pub use search_dao::{SearchHistoryDao, SqliteSearchHistoryDao};
 pub use user_ai_prefs_dao::{SqliteUserAiPrefsDao, UserAiPrefsDao};
+pub use version_dao::{SqliteVersionDao, VersionDao};
 
 pub trait UserDao {
     fn create_user(&mut self, user: &str, password: &str) -> Option<User>;