feat(db): add catalogue object update/delete with audited field diffs

update_object records only changed fields as audit diffs and skips the
audit entry for no-op updates; delete_object records a Deleted entry.
Both operations are atomic on the caller's connection.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/db/tests/catalog_mutations.rs

@@ -0,0 +1,123 @@
+use db::{Db, audit, catalog};
+use domain::{AuditAction, AuditActor, ObjectInput, Visibility};
+use sqlx::PgPool;
+
+fn base() -> ObjectInput {
+    ObjectInput {
+        object_number: "LM-1".into(),
+        object_name: "vase".into(),
+        number_of_objects: 1,
+        brief_description: None,
+        current_location: Some("shelf A1".into()),
+        current_owner: None,
+        recorder: None,
+        recording_date: None,
+        visibility: Visibility::Draft,
+    }
+}
+
+#[sqlx::test]
+async fn update_changes_are_audited_as_diffs(pool: PgPool) {
+    let db = Db::from_pool(pool);
+
+    let mut tx = db.pool().begin().await.unwrap();
+    let id = catalog::create_object(&mut tx, AuditActor::System, &base())
+        .await
+        .unwrap();
+    tx.commit().await.unwrap();
+
+    let mut changed = base();
+    changed.object_name = "roman vase".into();
+    changed.visibility = Visibility::Public;
+
+    let mut tx = db.pool().begin().await.unwrap();
+    let updated = catalog::update_object(&mut tx, AuditActor::System, id, &changed)
+        .await
+        .unwrap();
+    tx.commit().await.unwrap();
+    assert!(updated);
+
+    let obj = catalog::object_by_id(db.pool(), id).await.unwrap().unwrap();
+    assert_eq!(obj.object_name, "roman vase");
+    assert_eq!(obj.visibility, Visibility::Public);
+
+    let history = audit::history_for(db.pool(), "object", id.to_uuid())
+        .await
+        .unwrap();
+    assert_eq!(history.len(), 2); // created + updated
+    let update = &history[1];
+    assert_eq!(update.action, AuditAction::Updated);
+    let mut fields: Vec<&str> = update.changes.iter().map(|c| c.field.as_str()).collect();
+    fields.sort_unstable();
+    assert_eq!(fields, vec!["object_name", "visibility"]);
+}
+
+#[sqlx::test]
+async fn no_op_update_records_no_audit(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    let mut tx = db.pool().begin().await.unwrap();
+    let id = catalog::create_object(&mut tx, AuditActor::System, &base())
+        .await
+        .unwrap();
+    tx.commit().await.unwrap();
+
+    let mut tx = db.pool().begin().await.unwrap();
+    let updated = catalog::update_object(&mut tx, AuditActor::System, id, &base())
+        .await
+        .unwrap();
+    tx.commit().await.unwrap();
+    assert!(updated);
+
+    let history = audit::history_for(db.pool(), "object", id.to_uuid())
+        .await
+        .unwrap();
+    assert_eq!(
+        history.len(),
+        1,
+        "a no-op update must not add an audit entry"
+    );
+}
+
+#[sqlx::test]
+async fn update_missing_returns_false(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    let mut tx = db.pool().begin().await.unwrap();
+    let updated = catalog::update_object(
+        &mut tx,
+        AuditActor::System,
+        domain::ObjectId::new(),
+        &base(),
+    )
+    .await
+    .unwrap();
+    tx.commit().await.unwrap();
+    assert!(!updated);
+}
+
+#[sqlx::test]
+async fn delete_removes_and_audits(pool: PgPool) {
+    let db = Db::from_pool(pool);
+    let mut tx = db.pool().begin().await.unwrap();
+    let id = catalog::create_object(&mut tx, AuditActor::System, &base())
+        .await
+        .unwrap();
+    tx.commit().await.unwrap();
+
+    let mut tx = db.pool().begin().await.unwrap();
+    let deleted = catalog::delete_object(&mut tx, AuditActor::System, id)
+        .await
+        .unwrap();
+    tx.commit().await.unwrap();
+    assert!(deleted);
+
+    assert!(
+        catalog::object_by_id(db.pool(), id)
+            .await
+            .unwrap()
+            .is_none()
+    );
+    let history = audit::history_for(db.pool(), "object", id.to_uuid())
+        .await
+        .unwrap();
+    assert_eq!(history.last().unwrap().action, AuditAction::Deleted);
+}