CaService hard-requires STEP_CA_URL/provisioner config at construction, so an
unconditional FederationModule import makes every standalone/local boot die at
DI time. Gate the module on loadConfig().tier === federated, matching the
documented intent of the federation compose profile (must not start in
non-federated dev).
Verified in mosaic-dev box: standalone tier boots to "Gateway listening on
port 14242" with bootstrap/socket.io/auth surfaces responding; federated tier
path unchanged.
