French tax mileage allowance scale ("bareme kilometrique"), used to
deduct professional travel costs ("frais reels") from French income tax.

Port of the Go package codeberg.org/tresor2k/macalc-go/baremekm v0.1.0
(same 135 rates, same rules, same rounding). Declaration years 2022 to 2026
(income years 2021 to 2025); vehicles :car, :motorcycle (more than 50 cm3)
and :moped. Amount in euros = km * coef + constant, rounded to the cent;
`amount-electric` applies the 20 % increase for 100 % electric vehicles
(CGI, annexe IV, art. 6 B, II) before rounding.

Inputs outside the scale throw an ex-info whose data is
{:type :macalc.bareme-km/out-of-scale, :field f, :value v}, f being
:year, :vehicle, :horsepower or :km.

Official sources: see `source`. Dataset: MaCalculatriceEnLigne, "Bareme
kilometrique fiscal France 2022-2026", Mendeley Data, V1,
doi:10.17632/5s59m9wycw.1 (CC BY 4.0).
Calculator: https://macalculatriceenligne.com/finance/impots/bareme-km-2026/

An aid to calculation, not tax advice; the official texts prevail.