Web client posts Intl.DateTimeFormat().resolvedOptions().timeZone to
PUT /api/me/timezone after every successful login, register, and
bootstrap when the locally-stored tz_last_sent_at is >7 days old.
Cadence tracked in localStorage keeps the server stateless on the
"is this stale?" check.
Failures swallowed: the server's UTC default + last-known value keep
the scheduler functioning until the next successful attempt. SSR-
safe via the typeof window guard.
For #392 Half B. Companion Flutter change in next commit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusenandClaude Opus 4.7
6b7e4f1dee