Refactor a legacy freight tariff into structured output while preserving its quirks for old orders

# Refactor a legacy freight tariff without changing old invoices `legacy/tariff.py` is a 2019 script that prints one total per order from a pipe-separated file (`python legacy/tariff.py orders.txt`). Old invoices depend on its **exact** output, quirks included. Write `solve.py` (Python 3 standard library only): `python solve.py input.json answer.json`, where `input.json` has `orders` (each `id`, `date`, `zone`, `kg`, `declared`, `flags`; `orders.txt` holds the same orders in the legacy format). **The `legacy/` directory is deleted before scoring**, so `solve.py` must not import or run it. Fresh order sets are generated. ## Required behaviour 1. Orders dated **before 2027-01-01**: reproduce the legacy script exactly. That covers its `total` string and its `ERROR zone` cases, and every intermediate value as the legacy code computes it: billable kg, the rate it uses, base (after the express doubling), fuel, insurance, discount and the remote charge. Floating-point and formatting quirks included. 2. Orders dated **on or after 2027-01-01** follow the same legacy calculation, except: a. the zone rate is always the order's own zone rate (A, B or C; zone is case-insensitive), with no weight-based switch; any other zone is an error; b. flag `H` (hazmat) adds a flat 15.00 after everything else (not discounted). Before 2027 `H` is ignored, like any unknown flag. 3. Output per order, in input order: `{"id", "billable_kg", "rate", "base", "fuel", "insurance", "discount", "remote", "hazmat", "total"}` with numbers as JSON numbers and `total` as the string the legacy code would print (`"%.2f"`). An error order is `{"id", "error": "zone"}`. `hazmat` is 0 for orders without it, and `remote` is 9.99 or 0. ## answer.json `{"quotes": [...]}` ## Scoring Hidden checks (partial credit; all must pass; values must be equal exactly): `legacy_totals_preserved`, `legacy_breakdown` (pre-2027 orders), `new_rules_totals`, `new_rules_breakdown` (2027+ orders) on the given orders; `fresh_run_1`, `fresh_run_2` (all fields, all orders). 30-second limit per run.