GET /memories accepts reference_date=YYYY-MM-DD (a day in the owner's
display zone). It re-anchors both the span match (day_in_span's "today")
and the pre-filter window, which ends at the end of that day, so the
20-year lookback is measured from it and a future date surfaces
everything taken so far. Omitted → today, unchanged. Malformed → 400.
Reels stay anchored on now (MVP): the reel selector passes None.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>