Import a migration bundle

Performs a bulk import from a multipart upload containing a manifest JSON file and a zip of media files. In one operation, this creates the location tree, media library, playlists, and screens (initially unpaired) described by the manifest. Physical screens are paired into these pre-created entries later. Requires the import-create permission on the API key.

Notes.

• Re-importing the same manifest is safe: items it already created are counted as …Existing, not created again.
• All or nothing: a validation failure writes nothing.