PageScene: route shape recreate through the geometry key

Shapes redo'd to broken / invisible objects because the snapshot
captured obj.name = "Cube" (the display label addShape sets after
creation), but scene.instantiate's geometry switch only matches the
geometry key ("Box", "Sphere", "PointLight", ...). Calling
instantiate("Cube", pos) fell through with no matching geometry.

Fix: addShape stashes the geometry key in userData.shapeKey before
overriding obj.name. recreateFromSnapshot picks shapeKey when
present (falls back to snap.name for non-shape paths), then restores
obj.name = snap.name after the create returns so the display label
sticks. Non-shape recreations are unaffected — their userData has no
shapeKey, so the fallback to snap.name keeps the existing flow.

frontend/apps/artcraft/app/src/pages/PageScene/actions/addShape.ts

@@ -15,6 +15,10 @@ export async function addShape(
     position ?? new THREE.Vector3(),
   );
   if (!obj) return undefined;
+  // Stash the geometry key (Box / Sphere / PointLight / ...) so undo/redo
+  // can re-route through scene.instantiate's name switch. obj.name gets
+  // overridden below with the display label ("Cube", "Point Light").
+  obj.userData.shapeKey = item.media_id;
   obj.name = item.name ?? "shape";
 
   editor.history.record(new CreateAction(editor, obj));

frontend/apps/artcraft/app/src/pages/PageScene/engine/editor/actions/snapshots.ts

@@ -71,9 +71,22 @@ export const recreateFromSnapshot = async (
     snap.transform.position.y,
     snap.transform.position.z,
   );
-  const obj = await editor.sceneManager?.create(snap.media_id, snap.name, pos);
+  // Shapes route through scene.instantiate's geometry switch, which
+  // matches on the geometry key ("Box", "Sphere", "PointLight"), not
+  // the display name ("Cube", "Point Light"). addShape stashes the
+  // original key in userData.shapeKey so we can recover it here.
+  const nameForCreate =
+    (snap.userData.shapeKey as string | undefined) ?? snap.name;
+  const obj = await editor.sceneManager?.create(
+    snap.media_id,
+    nameForCreate,
+    pos,
+  );
   if (!obj) return undefined;
   obj.uuid = snap.uuid;
+  // Restore the display name (instantiate/loadObject set obj.name to
+  // nameForCreate; for shapes that's the geometry key, not the label).
+  obj.name = snap.name;
   obj.rotation.set(
     snap.transform.rotation.x,
     snap.transform.rotation.y,