A partial update that left day_id out (a notes-only PUT, an MCP
update_reservation or update_transport call) re-derived the day from the
stored reservation_time whenever one was set. A time-only value such as
"12:00" resolves to no day, so the booking's day_id was written as null and
it vanished from its day in the planner. The end_day_id branch did the same
when a time-only reservation_end_time was sent.
The day is now derived only when the time carries a date that resolves to a
trip day; otherwise an omitted day_id or end_day_id keeps the stored value.
A dated time still re-pins the day, an explicit day_id null still clears it,
and a cleared end time still clears end_day_id. REST and both MCP update
tools share updateInTx, so the fix covers all three.
Tests: service unit cases (RESV-SVC-044..048), an e2e case per behaviour
on PUT /api/trips/:tripId/reservations/:id, and an update_reservation MCP
case, all seeded with the ORM factories.
Fixes#3025
John Jahn
8e8cff8105