Write the STEG tariff figures in one place

In plain terms. The official STEG figures — price per kWh tranche, the 700 millimes/kVA, the 5 millimes of CL and FTE, the VAT rates — are currently copied inside every page that mentions them. No single place says "here is the tariff"; each page carries its own copy.

Why it matters, demonstrated this week. The redevance error ("700 millimes" instead of "700 per kVA") existed twice: on /tarifs and on /steg/facture. One wrong fact took two fixes — and someone had to think to look for the second. The bill calculator would have made a third copy.

The day STEG revises its tariffs, someone updates one page and forgets the other, and the site shows two different prices for the same kWh — worse than being out of date: visibly incoherent about the one thing it is meant to know best.

The ask. Allow moving those figures into a single data file that every page reads. No visible change for a visitor. The cost is technical work on /tarifs, a page that performs (position 4.0) — hence a question rather than a decision taken alone.

Side benefit: that file can carry a last-verified date, so pages could show "tariff verified on …" — a trust signal no Tunisian competitor offers.

Answer (2026-08-19, Fred): "Sure move the number to /departments, it doesn't change anything for the content anyway, right? Just reusing the same config/file everywhere?" — correct on both counts: same figures, same rendering, one source. Shipped as #16283.

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