The Apple Health batch endpoint accepted 500-row payloads with no
per-user write cap. A leaked wildcard iOS token could sustain
unbounded inserts (500 rows × N batches/sec) and degrade the
database for every other user on the host.
Gate the write path with the shared `checkRateLimit` helper at
60 batches/min/user — generous for legitimate iOS sync (the
HealthKit observer coalesces well below one batch/minute on a
quiet device, and 60/min × 500 rows = 30 000 rows/min headroom)
and tight enough that a misbehaving client bottoms out within a
minute. Returns 429 with an unambiguous message so the iOS
client can back off and retry rather than assume the row landed.
Integration test exercises the over-limit path by pre-seeding the
`rate_limits` counter at the cap.
Marc-André Bombeck
04dd972358