feat(db): add object.fields jsonb column, read it into CatalogueObject

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/db/src/catalog.rs

@@ -15,7 +15,7 @@ const ENTITY_TYPE: &str = "object";
 
 const OBJECT_COLUMNS: &str = "id, object_number, object_name, number_of_objects, \
      brief_description, current_location, current_owner, recorder, recording_date, \
-     visibility, created_at, updated_at";
+     visibility, fields, created_at, updated_at";
 
 /// Create an object and record a `created` audit entry, both on `conn`
 /// (pass a transaction connection `&mut *tx` so they commit atomically).
@@ -110,6 +110,7 @@ fn map_object(row: sqlx::postgres::PgRow) -> Result<CatalogueObject, sqlx::Error
         recorder: row.try_get("recorder")?,
         recording_date: row.try_get("recording_date")?,
         visibility,
+        fields: row.try_get("fields")?,
         created_at: row.try_get("created_at")?,
         updated_at: row.try_get("updated_at")?,
     })