UUri has no usable API

It's just an empty struct. Missing:
- __repr__ / __str__ — no way to see what URI it represents
- authority_name(), resource_id(), uentity_*() accessors
- is_empty(), is_remote(), matches() predicates
- from_str() / to_uri() serialization

Start by locating the empty UUri struct and the Python binding entry point. Use the issue's method list as the checklist, then inspect the surrounding project conventions before implementing the accessors, predicates, display methods, and serialization; done means each listed operation is usable and covered by tests.

Written by the indexing model from the issue text.