- albums.owner_id (migration 0003, backfilled to the original user)
- owned::{album,photo,share} are the only admin data-access paths; another
tenant's resources are indistinguishable from nonexistent (404)
- every admin handler threaded through ownership; each ALLOWED_EMAILS entry
is now its own isolated workspace
- tenant-isolation integration test matrix (tests/tenancy.rs, env-gated on
TEST_DATABASE_URL) driving the real router
