v0.1.6 — doctor pre-flight check + discovery-version guard

Pre-pump operability, and a compatibility hardening from the public-config research.

Added

• npm run doctor (#28) — a pre-flight self-check to run the moment a new pump pairs. Confirms .env is complete, decodes and reports your login token's validity/expiry, and checks that CareLink and Nightscout are both reachable with an accepted API_SECRET — without fetching pump data. One request each to two hosts, safe to run repeatedly; non-zero exit on failure so it can gate a deploy. First item of the v0.2.0 operability set (#8).

Changed

• Discovery app-version pinned as a documented constant (#27). Live probing showed Medtronic's discovery endpoint returns a different config per app-version string — only android/3.6/3.7 carry the Auth0 SSO config this flow needs (3.4 and 4.0 return no-Auth0 tracks) — so bumping it to a "newer" number would silently break login. The failure now names the version string as the likely cause.

55/55 tests on Node 20 + 22. No new dependencies. Still no real-CareLink validation — that waits on the pump (#12).