When Redis cache is populated from DB with a NULL window_1d_start, the
Lua increment script only updates usage counters without setting window
timestamps. IsWindowExpired(nil) previously returned false, so the
accumulated usage was never reset across time windows, effectively
turning usage_1d into a lifetime counter. Once this exceeded
rate_limit_1d the key was incorrectly blocked with "日限额已用完".
FixesWei-Shaw/sub2api#1022