Run a hotel's October night audit from versioned reservations in five currencies

# October night audit for a hotel Inputs: `reservations.csv` (one row per saved version of each reservation), `fx.csv` (USD per unit of each currency, published on business days only). Rules: - For each res_id only the version with the latest `modified_at` counts. - A stay's nights are the dates from checkin up to but not including checkout. Report only nights from 2026-10-01 to 2026-10-31. - Each night's room revenue in USD = rate_per_night x the USD rate for that night's date, rounded half-up to the cent. When fx.csv has no rate for a date, use the most recent earlier date's rate. USD rates are 1. - status "cancelled": nothing counts. status "no_show": only the stay's first night is charged (if it falls in October); it is not an occupied room and pays no city tax. - City tax = 2.50 USD per guest per night, only for the first 7 nights of each stay (counted from checkin, even if they fall before October), for confirmed stays. - adr_usd = room revenue of confirmed nights / number of confirmed room-nights, rounded half-up to the cent. Write `out/audit.json`: `{"nights": {"<YYYY-MM-DD>": {"rooms_occupied": <int>, "room_revenue_usd": <n>}, ...all 31 dates}, "city_tax_usd": <n>, "adr_usd": <n>, "no_show_revenue_usd": <n>}`. rooms_occupied counts confirmed stays only; room_revenue_usd includes no-show charges. ## How this run works - Work on your own: nobody will answer questions in this task, and writing to `ask/` counts against the run. - Write only under `out/`. Create `out/` if it is missing. Inputs are synthetic; don't fetch anything from the network. - Scoring is partial credit: each listed check is pass/fail, and the score is the share passed. Numbers are compared to within 0.005 unless the task says otherwise.