support aquiring server props and test dropping them

crates/chattyness-db/src/queries/loose_props.rs

@@ -8,6 +8,30 @@ use uuid::Uuid;
 use crate::models::{InventoryItem, LooseProp};
 use chattyness_error::AppError;
 
+/// Ensure an instance exists for a scene.
+///
+/// In this system, scenes are used directly as instances (channel_id = scene_id).
+/// This creates an instance record if one doesn't exist, using the scene_id as the instance_id.
+/// This is needed for loose_props foreign key constraint.
+pub async fn ensure_scene_instance<'e>(
+    executor: impl PgExecutor<'e>,
+    scene_id: Uuid,
+) -> Result<(), AppError> {
+    sqlx::query(
+        r#"
+        INSERT INTO scene.instances (id, scene_id, instance_type)
+        SELECT $1, $1, 'public'::scene.instance_type
+        WHERE EXISTS (SELECT 1 FROM realm.scenes WHERE id = $1)
+        ON CONFLICT (id) DO NOTHING
+        "#,
+    )
+    .bind(scene_id)
+    .execute(executor)
+    .await?;
+
+    Ok(())
+}
+
 /// List all loose props in a channel (excluding expired).
 pub async fn list_channel_loose_props<'e>(
     executor: impl PgExecutor<'e>,
@@ -106,8 +130,8 @@ pub async fn drop_prop_to_canvas<'e>(
                 instance_id as channel_id,
                 server_prop_id,
                 realm_prop_id,
-                ST_X(position) as position_x,
-                ST_Y(position) as position_y,
+                ST_X(position)::real as position_x,
+                ST_Y(position)::real as position_y,
                 dropped_by,
                 expires_at,
                 created_at