file_storage: list/get/download/visibility endpoints have no owner check (any user role sees every file) #544

modules/file_storage/file_storage/endpoints/api.py list_files, get_file, download_file and update_file (→ visibility.set_public) are gated only by permission (file_storage.download / upload) plus the tenant filter. The platform user role carries UPLOAD and DOWNLOAD (module.py register_permissions), and on a single-tenant install every row is in DEFAULT_TENANT_ID, so any user-role account can list and download every stored file and toggle any file public — including other users' uploads and branding assets.

Fix direction: decide the intended model. Likely: non-admin callers see and change only rows they created (created_by == principal), and file_storage.manage (or admin) sees all. Apply the scope in the service query so list/count/get agree, and add tests with two ordinary users.

Found in the security review of #525.

https://claude.ai/code/session_01M9neheZZEe3sVpDi2S3zT4