predictalot v0.2.1 — require auth on /v1/<type>/models

Security patch. Closes a usage-pattern info leak: with auth
configured, the per-type GET /v1/<type>/models endpoints shipped
in v0.2.0 were missing the Depends(check_bearer) guard and would
return the installed model list, loaded state, and last-used
timestamps to unauthenticated callers. Now bearer-protected. The
/healthz endpoint stays open. Open-auth deployments
(PREDICTALOT_ALLOW_NO_AUTH=1 + empty token list) are unaffected.