Root cause (found in the live DB): register_at() returned the latest reading
for any boundary beyond the DSMR data range (a future instant or a long gap),
so future periods got start==end -> delta 0 and were written as degraded=False
'ok' rows with cost 0. recompute_range() over a future end then filled the whole
month with such fake rows, which then occupied the slots so the per-minute tick
(immutability guard skips non-degraded rows) never recomputed the real data.
- register_at: ignore a reading older than one period (15min) before the
boundary -> returns None -> period is marked degraded instead of a fake 0.
- recompute_range: only process closed periods (t1 <= now); never future ones.
- Tests cover staleness window, out-of-range -> degraded, recompute skips
future, and a regression that normal closed periods are unaffected.
tliu93
9d3e28a529