faces: PATCH/POST /image/faces returns person_name with the row

Both create_face_handler and update_face_handler returned the bare
FaceDetectionRow, so PATCH /image/faces/{id} (used by both bbox edits
and person assignment) replied without person_name. The carousel
overlay does an optimistic replace on this row — replacing the joined
FaceWithPerson with a row that has person_name = undefined visibly
dropped the VFD label off the bbox after every save.

Add a small hydrate_face_with_person helper that does the persons
lookup and assembles a FaceWithPerson, used by both handlers. The
list endpoint already does the join, so the PATCH/POST shape now
matches it.

src/faces.rs

@@ -117,6 +117,35 @@ struct InsertFaceDetection {
     created_at: i64,
 }
 
+/// Build a [`FaceWithPerson`] from a freshly-mutated row by resolving the
+/// person name via [`FaceDao::get_person`]. Used by `create_face_handler`
+/// and `update_face_handler` so PATCH/POST responses match the join shape
+/// `/image/faces` returns — without this the carousel overlay's
+/// optimistic-replace would clobber the rendered name (the bare
+/// [`FaceDetectionRow`] doesn't carry it).
+fn hydrate_face_with_person<D: FaceDao>(
+    dao: &mut D,
+    ctx: &opentelemetry::Context,
+    row: FaceDetectionRow,
+) -> anyhow::Result<FaceWithPerson> {
+    let person_name = match row.person_id {
+        Some(pid) => dao.get_person(ctx, pid)?.map(|p| p.name),
+        None => None,
+    };
+    Ok(FaceWithPerson {
+        id: row.id,
+        bbox_x: row.bbox_x.unwrap_or(0.0),
+        bbox_y: row.bbox_y.unwrap_or(0.0),
+        bbox_w: row.bbox_w.unwrap_or(0.0),
+        bbox_h: row.bbox_h.unwrap_or(0.0),
+        confidence: row.confidence.unwrap_or(0.0),
+        source: row.source,
+        person_id: row.person_id,
+        person_name,
+        model_version: row.model_version,
+    })
+}
+
 /// Face row decorated with its assigned person's name. Returned by
 /// `/image/faces` for the rendering side (carousel overlay, person chips).
 #[derive(Serialize, Debug, Clone)]
@@ -2099,7 +2128,10 @@ async fn create_face_handler<D: FaceDao>(
         "Created manual face id={} library={} hash={} person_id={:?}",
         row.id, row.library_id, row.content_hash, row.person_id
     );
-    HttpResponse::Created().json(row)
+    match hydrate_face_with_person(&mut *dao, &span_context, row) {
+        Ok(joined) => HttpResponse::Created().json(joined),
+        Err(e) => HttpResponse::InternalServerError().body(e.to_string()),
+    }
 }
 
 async fn update_face_handler<D: FaceDao>(
@@ -2205,8 +2237,16 @@ async fn update_face_handler<D: FaceDao>(
     }
 
     let mut dao = face_dao.lock().expect("face dao lock");
-    match dao.update_face(&span_context, id, person_patch, bbox_patch, new_embedding) {
+    let row = match dao.update_face(&span_context, id, person_patch, bbox_patch, new_embedding) {
-        Ok(row) => HttpResponse::Ok().json(row),
+        Ok(r) => r,
+        Err(e) => return HttpResponse::InternalServerError().body(e.to_string()),
+    };
+    // Hydrate person_name so the response shape matches GET /image/faces
+    // — the carousel overlay does an optimistic replace on this row, and
+    // a bare FaceDetectionRow with no person_name would visibly drop the
+    // VFD label off the bbox even though the assignment didn't change.
+    match hydrate_face_with_person(&mut *dao, &span_context, row) {
+        Ok(joined) => HttpResponse::Ok().json(joined),
         Err(e) => HttpResponse::InternalServerError().body(e.to_string()),
     }
 }