v2.3.0 — Cost Live MTD History (15-min Snapshot Archive + EOD Reconstruction)

See CHANGELOG.md for the full narrative.

Added

• MTD snapshot archive + history view on Cost Live — the Spend Limits API has no history parameters, so the server now archives each org's payload to S3 every 15 minutes (spend_mtd/date=…/HHMM.json, 15-min slots dedupe the two Fargate tasks). New /api/cost/spend-limits/snapshots + /at endpoints; the page gains a date picker, archived-times dropdown, snapshot stamp, and a Back-to-Live button (auto-refresh freezes on history views). Intraday history begins at this deploy.
• End-of-day reconstruction for pre-archive dates — approximated from user_cost_report (month-start → date, approx: true banner; no limits/utilization). Verified against cost_report's month total to the cent.

Fixed (caught by the pre-deploy adversarial review)

• View-transition payload mismatch — old numbers no longer flash under a new view's labels.
• "Live" badge no longer renders on archived/reconstructed views.

Changed

• Cost Live wording: near-real-time/거의 실시간 → real-time/실시간.