feat(legal): bilingual (RU + EN) legal pages with a language + theme switcher

Add English versions of the privacy policy, EULA and offer (ui/legal/*_en.md) and render each legal page as one self-contained bilingual document: both language bodies plus a header language toggle and theme toggle (no back), a small inline ES5 script that switches language client-side (no reload, default Russian + persisted) and applies the theme (system default + persisted override) — mirroring the landing. The offer's English view transliterates the Russian product names spliced from the live catalog.

renderLegalHtml now takes both language sources; renderOffer splices the price list into both; the renderer bakes and reads the _en sources and pre-renders the static pages at boot. Also wrap the /offer/ contour probe in the same retry+timeout as the legal probe (the offer page is now bilingual and larger). Docs + renderer/ui tests updated.

renderer/src/offer.mjs

@@ -1,17 +1,21 @@
-// The public-offer page renderer: splices the live catalog price list into the owner-edited offer
-// markdown and renders it with the SAME renderOfferHtml the landing build used to invoke (bundled
-// from ui/src/lib/offer). Kept out of server.mjs so the substitution is unit-testable without HTTP.
+// The public-offer page renderer: splices the live catalog price list into BOTH language sources of
+// the owner-edited offer markdown at the pricing marker, and renders the bilingual /offer/ page with
+// the SAME renderOfferHtml the browser build uses (bundled from ui/src/lib/offer). The English view
+// transliterates the Russian product names client-side (renderLegalHtml). Kept out of server.mjs so
+// the substitution is unit-testable without HTTP.
 import { renderOfferHtml } from '../dist/gameimage.mjs';
 
-// pricingMarker is the token ui/legal/offer_ru.md carries at §4.4 where the price list belongs. It
+// pricingMarker is the token ui/legal/offer_{ru,en}.md carry at §4.4 where the price list belongs. It
 // mirrors the backend marker (backend/internal/payments/offer.go) and is replaced with the fetched
 // tables before rendering.
 export const pricingMarker = '<#pricing_template#>';
 
-// renderOffer returns the standalone /offer/ HTML: the offer markdown with the pricing marker
+// renderOffer returns the standalone /offer/ HTML: the RU + EN offer markdown with the pricing marker
 // replaced by pricingTables (the two markdown tables the backend projects from the active catalog),
-// rendered to a self-contained document. The replacement is literal (a function replacer) so a "$"
-// in a product title is never read as a replacement pattern; a missing marker leaves the text as is.
-export function renderOffer(offerMarkdown, pricingTables) {
-  return renderOfferHtml(offerMarkdown.replace(pricingMarker, () => pricingTables));
+// rendered to a self-contained bilingual document. The replacement is literal (a function replacer)
+// so a "$" in a product title is never read as a replacement pattern; a missing marker leaves the
+// text as is.
+export function renderOffer(ruMarkdown, enMarkdown, pricingTables) {
+  const splice = (md) => md.replace(pricingMarker, () => pricingTables);
+  return renderOfferHtml(splice(ruMarkdown), splice(enMarkdown));
 }