One-command node onboarding installer (auth = org API key bearer, OR a pre-minted provisioning token via ?token=)

Returns a self-contained shell installer (curl | sudo bash). With a bearer org API key it mints a fresh single-use provisioning token; with ?token=vtk_… (e.g. minted from the dashboard) it self-auths and embeds that token instead. name only applies when minting (the token already carries it). Nodes always enroll as QEMU VM hosts in the community pool.