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/schema.rs

@@ -345,6 +345,33 @@ diesel::table! {
     }
 }
 
+diesel::table! {
+    photo_version_display (original_hash) {
+        original_hash -> Text,
+        display_hash -> Text,
+        decided_at -> BigInt,
+    }
+}
+
+diesel::table! {
+    photo_version_references (version_hash, reference_hash) {
+        version_hash -> Text,
+        reference_hash -> Text,
+    }
+}
+
+diesel::table! {
+    photo_versions (version_hash) {
+        version_hash -> Text,
+        original_hash -> Text,
+        kind -> Text,
+        source -> Text,
+        created_at -> BigInt,
+        library_id -> Integer,
+        rel_path -> Text,
+    }
+}
+
 diesel::table! {
     precomputed_reels (id) {
         id -> Integer,
@@ -392,6 +419,9 @@ diesel::allow_tables_to_appear_in_same_query!(
     personas,
     persons,
     photo_insights,
+    photo_version_display,
+    photo_version_references,
+    photo_versions,
     precomputed_reels,
     search_history,
     tagged_photo,