First-gen Withings Thermo (WBT01) reports body temperature under
meastype 12. The current-gen Thermo ships meastype 71 (next commit).
Both decode through the same `value * 10^unit` path the client already
applies, and target the `BODY_TEMPERATURE` enum slot we added in v1.4.23
for the Apple Health passthrough.
Adds `src/lib/withings/__tests__/client.test.ts` with a synthetic
`getmeas` payload covering the exponent decode, unknown-meastype skip,
and two-decimal rounding. Re-exports MEASURE_TYPE_MAP so the test can
assert the mapping directly without importing internals.
Marc-André Bombeck
ae8e2d77aa