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/README.md

@@ -4,7 +4,8 @@ An internal Node service that runs shared `ui/src/lib` renderers server-side —
 image build time (`src/entry.ts` → esbuild → `dist/gameimage.mjs`) so there is one renderer and no
 drift from the browser. It serves two surfaces: the finished-game export **PNG** (on
 [skia-canvas](https://github.com/samizdatco/skia-canvas), pixel-identical to the design the owner
-signed off) and the public **legal pages** (the offer, the privacy policy and the EULA).
+signed off) and the public **legal pages** (the offer, the privacy policy and the EULA), each
+bilingual (RU + EN) with a language + theme switcher.
 
 ## Interface
 
@@ -16,13 +17,16 @@ signed off) and the public **legal pages** (the offer, the privacy policy and th
 - `GET /offer/` — the public offer page as `text/html`: the owner-edited `ui/legal/offer_ru.md`
   (baked into the image, read at boot) with the live catalog **price list** (§4.4) fetched as
   markdown from the backend's internal `/api/v1/internal/offer/pricing` (`RENDERER_BACKEND_URL`)
-  and spliced in at the `<#pricing_template#>` marker, then rendered by the shared
-  `ui/src/lib/offer.ts` `renderLegalHtml`. `GET /offer` → 301 `/offer/`. Caddy routes `/offer/`
-  here; a backend outage yields a 502, never a stale price list.
+  and spliced in at the `<#pricing_template#>` marker of both language sources (`offer_ru.md` /
+  `offer_en.md`), then rendered as one bilingual page by the shared `ui/src/lib/offer.ts`
+  `renderLegalHtml` (the English view transliterates the Russian product names client-side).
+  `GET /offer` → 301 `/offer/`. Caddy routes `/offer/` here; a backend outage yields a 502, never a
+  stale price list.
 - `GET /privacy/` — the privacy policy, and `GET /eula/` the end-user licence agreement, both as
-  `text/html`: the owner-edited `ui/legal/privacy_ru.md` / `ui/legal/eula_ru.md` (baked in, read at
-  boot), rendered once at boot by the same shared `renderLegalHtml` and served from cache. **Static** — no backend fetch. `GET /privacy`
-  / `GET /eula` → 301 to the trailing-slash form. Caddy routes these here too.
+  `text/html`: the owner-edited `ui/legal/{privacy,eula}_{ru,en}.md` (baked in, read at boot),
+  rendered once at boot as one bilingual page by the same shared `renderLegalHtml` and served from
+  cache. **Static** — no backend fetch. `GET /privacy` / `GET /eula` → 301 to the trailing-slash
+  form. Caddy routes these here too.
 - `GET /healthz` — liveness (the compose healthcheck the backend's `depends_on` gates on).
 
 The service renders and nothing else: for the PNG, authentication, the participant check and the
@@ -40,8 +44,10 @@ pnpm test             # bundles, then node --test (PNG smoke + offer/legal rende
 # local run on :8090 (RENDERER_PORT overrides). The server reads all three legal sources at boot, so
 # point each at its ui/legal source (the baked paths do not exist in a local checkout); /offer/ also
 # needs a reachable backend for the price fetch:
-RENDERER_OFFER_MD=../ui/legal/offer_ru.md RENDERER_PRIVACY_MD=../ui/legal/privacy_ru.md \
-  RENDERER_EULA_MD=../ui/legal/eula_ru.md RENDERER_BACKEND_URL=http://localhost:8080 node src/server.mjs
+RENDERER_OFFER_MD=../ui/legal/offer_ru.md RENDERER_OFFER_EN_MD=../ui/legal/offer_en.md \
+  RENDERER_PRIVACY_MD=../ui/legal/privacy_ru.md RENDERER_PRIVACY_EN_MD=../ui/legal/privacy_en.md \
+  RENDERER_EULA_MD=../ui/legal/eula_ru.md RENDERER_EULA_EN_MD=../ui/legal/eula_en.md \
+  RENDERER_BACKEND_URL=http://localhost:8080 node src/server.mjs
 ```
 
 The runtime image (`renderer/Dockerfile`, `node:22-slim`) bakes in Liberation Sans (the