Marc-André Bombeck 71745b4c63 fix(analytics): thread user timezone through the weight-weekday correlator ...

The W7 per-user-tz sweep threaded `userTz` through every aggregator on
the analytics route except `berlinIsoWeekday()` — the module-level
`Intl.DateTimeFormat` stayed pinned to `Europe/Berlin`. A user in
`Pacific/Auckland` whose 23:30 weight reading lands at 12:30 the same
day in Berlin had their Monday-local reading bucketed under Sunday's
weekday column. Pearson/ANOVA on the wrong weekday.

Replace the pinned formatter with a per-tz memoised lookup, rename the
helper to `isoWeekdayInTz()`, and feed `userTz` through the call site.
Also rename the misleading `dateFromBerlinKey()` → `dateFromDayKey()`
since the keys it consumes are already anchored to the user's tz
upstream.

Integration test covers the non-Berlin path: 28 weight readings at a
UTC instant where the Berlin and Auckland weekdays disagree; the
correlator reaches the gate with every seeded row counted, confirming
the helper used the user's tz to bucket.

2026-05-14 16:48:46 +02:00

..

integration

fix(analytics): thread user timezone through the weight-weekday correlator

2026-05-14 16:48:46 +02:00