Fill the matter-open form

A lawyer-tier account reaches the form at /app/projects/new. It asks for a name, a code, an Entity, a description, scope of services, the client DRI, and a required conflict-check attestation. Navigator stores the code exactly as typed — the code is immutable, and a code already in use by another matter is refused rather than silently resolved, because it is a coordinate the caller already committed to elsewhere (a repository's navigator.yaml, a Drive folder name).