Adds the integration suite for the detection worker against a real
Postgres testcontainer. Covers measurement-driven PRs (steps,
RHR, VO2 max), idempotency on re-run, silent-flag propagation,
and the drift guard that every PR-trackable metric type lands in
the scan loop.
Also patches a pre-existing schema gap: the
(userId, metricType, metricSlot, achievedAt) unique index on
personal_records is NULLS-DISTINCT in Postgres, so the index alone
does not dedup the measurement-driven rows (metricSlot = NULL).
The worker now does an application-level pre-flight findFirst on
the same composite key before each insert, keeping both the
workout path (index covers it) and the measurement path
(application-level guard) idempotent without a Migration.
Marc-André Bombeck
223b8a9208