fix(exchange): in-flight reservations disappear from daily headroom at UTC rollover #657

Summary

Active RI exchange reservations can stop counting at midnight UTC before their execution settles. This is separate from the same-day AUTO concurrency fix in LeanerCloud/cloud-commitments-go#41.

Current behaviour

At platform baseline 3131779, internal/config/store_postgres.go:3059-3065 sums completed and processing rows only when COALESCE(completed_at,updated_at) lies inside the requested UTC day. The go#41 atomic reservation change reuses this daily-window policy, so an unsettled prior-day processing row remains excluded after rollover.

Steps to verify the gap

Use a frozen clock, fixture execution and real local PostgreSQL; do not make purchases. Hold a day-A AUTO reservation of1000 in execution across midnight. A day-B daily read sees zero from that hold and permits another1000 reservation. If both fresh quotes settle for950 on dayB, the day-B accepted total becomes1900 under cap1000. This is a code-derived scenario, not an observed production purchase.

Expected behaviour

Active reservations remain counted conservatively until reconciled, including across UTC midnight. Completed prior-day spend resets according to a clearly defined acceptance-day policy.

Proposed fix and acceptance

Define acceptance-day accounting and keep active processing holds included across rollover under the same global reservation lock. Add frozen-clock real-database coverage spanning midnight, exact UTC boundaries, completed prior-day reset and active-hold retention. Relevant path: internal/config/store_postgres.go, GetRIExchangeDailySpend and atomic ReserveRIExchange.

References and severity

Refs LeanerCloud/cloud-commitments-go#41. High severity when triggered; limited timing-dependent impact. No failing regression or production incident is claimed by this tracking issue.