fix(versions): review findings on PR #193

- A version no longer hides behind an original that duplicates resolve
  demoted (visible_version_clause, hidden_version_rows).
- Recording a link drops the version's faces, CLIP data and clip failures
  (covers link-at-ingest and link_versions --apply).
- The display file must live in the original's library; otherwise the
  original shows, and PUT /image/versions/display answers 400.
- link_new_files looks up hashes in chunks of 500 and logs errors.

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

src/versions/handlers.rs

@@ -159,9 +159,16 @@ pub fn build_response(
         });
     }
 
-    let display_hash = dao
-        .get_display(original_hash)?
-        .filter(|d| versions.iter().any(|v| &v.hash == d));
+    // Clients fetch the display file through the original's library, so a
+    // choice with no row there reads as the original (as `/photos` does).
+    let display_hash = dao.get_display(original_hash)?.filter(|d| {
+        versions.iter().any(|v| {
+            &v.hash == d
+                && original
+                    .as_ref()
+                    .is_none_or(|o| o.library_id == v.library_id)
+        })
+    });
     Ok(VersionsResponse {
         original,
         versions,
@@ -232,6 +239,16 @@ pub async fn put_display(
         if !current.versions.iter().any(|v| v.hash == hash) {
             return HttpResponse::BadRequest().body("display_hash is not a version of this photo");
         }
+        // The display file is fetched through the original's library.
+        let original_lib = current.original.as_ref().map(|o| o.library_id);
+        if !current
+            .versions
+            .iter()
+            .any(|v| v.hash == hash && original_lib.is_none_or(|l| l == v.library_id))
+        {
+            return HttpResponse::BadRequest()
+                .body("display_hash has no file in the original's library");
+        }
     }
     if let Err(e) = dao.set_display(&resolved.original_hash, wanted) {
         warn!("put_display failed: {:?}", e);