InvitationResponse was missing project_name and invited_by_username fields,
causing /invitations accept to redirect to /project/undefined.
Now populated via async from_model() with batch DB lookups.
Add ssh_clone_url and https_clone_url to ProjectRepositoryItem,
constructed from config.ssh_domain() and config.git_http_domain().
Update frontend RepoInfo interface and header.tsx to use the
server-provided URLs instead of hardcoded values.
