feat(offer): live catalog price list in the public offer, served by the render sidecar

Robokassa moderation requires the public offer to list every digital good with
its price. Move /offer/ off the static landing container to the render sidecar:
it splices the live catalog price list (§4.4) into the owner-edited
ui/legal/offer_ru.md and renders it with the shared ui/src/lib/offer.ts — one
renderer, no drift, always matching the current catalog with no redeploy.

- backend: /api/v1/internal/offer/pricing (internal, off the edge allow-list)
  projects the active catalog into two markdown tables — chip packs priced per
  rail (roubles / VK votes / Telegram Stars) and chip-priced values — through
  payments.Money so no float reaches the page. Cached in memory: warmed at boot,
  marked stale on every catalog mutation, so a served render issues no query.
- renderer: GET /offer/ fetches the tables and substitutes them at the
  <#pricing_template#> marker, then renders; offer_ru.md is baked into the image
  and marked is bundled from ui. GET /offer -> 301. Only /offer/ is edge-exposed.
- caddy: route /offer/ to the sidecar; drop the now-dead landing /offer/
  handlers and the vite emit-offer plugin.
- offer: fill §4.3 (the chip-payment wording) and drop the in-page back link.
- landing footer: a feedback link (the offer's Telegram contact) beside the
  offer link.
- docs (ARCHITECTURE, FUNCTIONAL +_ru, renderer README), CI /offer/ probe,
  unit + integration + node tests.

ui/src/Landing.svelte

@@ -125,7 +125,13 @@
   </section>
 
   <footer class="ft">
-    <a class="offer" href="/offer/">{t('landing.offer')}</a>
+    <span class="legal">
+      <a class="offer" href="/offer/">{t('landing.offer')}</a>
+      <span class="sep" aria-hidden="true">|</span>
+      <!-- The feedback bot: the same Telegram contact the offer lists (section 11 «Реквизиты»);
+           external, opens in a new tab. -->
+      <a class="offer" href="https://t.me/Erudit_GameBot" target="_blank" rel="noopener noreferrer">{t('landing.feedback')}</a>
+    </span>
     <span>{t('about.version', { v: __APP_VERSION__ })}</span>
   </footer>
 </main>
@@ -287,6 +293,14 @@
     color: var(--text-muted);
     font-size: 0.8rem;
   }
+  .ft .legal {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+  }
+  .ft .sep {
+    color: var(--text-muted);
+  }
   .ft .offer {
     color: inherit;
   }

ui/src/lib/i18n/en.ts

@@ -285,6 +285,7 @@ export const en = {
   'landing.captionVK': 'VK',
   'landing.captionWeb': 'Web',
   'landing.offer': 'Public offer',
+  'landing.feedback': 'Feedback',
 
   'install.title': 'Install the app',
   'install.subtitle': 'Put the app icon on your desktop (home screen) to open the game in one tap.',

ui/src/lib/i18n/ru.ts

@@ -285,6 +285,7 @@ export const ru: Record<MessageKey, string> = {
   'landing.captionVK': 'VK',
   'landing.captionWeb': 'Веб-версия',
   'landing.offer': 'Публичная оферта',
+  'landing.feedback': 'Обратная связь',
 
   'install.title': 'Установить приложение',
   'install.subtitle': 'Поместите иконку приложения на рабочий стол (домашний экран), чтобы открывать игру одним нажатием.',

ui/src/lib/offer.test.ts

@@ -10,8 +10,8 @@ describe('renderOfferHtml', () => {
     // The markdown heading is rendered, not left as literal source.
     expect(html).toContain('<h1>Публичная оферта</h1>');
     expect(html).not.toContain('# Публичная оферта');
-    // A back link to the landing root is always present.
-    expect(html).toContain('href="/"');
+    // No in-page navigation: the standalone offer carries no "back" link.
+    expect(html).not.toContain('class="back"');
   });
 
   it('renders headings, bold clause numbers and lists', () => {

ui/src/lib/offer.ts

@@ -2,13 +2,15 @@ import { marked } from 'marked';
 
 /**
  * renderOfferHtml renders the public-offer markdown source into a standalone,
- * self-contained HTML document served statically at `/offer/`. The build emits
- * the result as `dist/offer/index.html` (see the `emit-offer` plugin in
- * `vite.config.ts`), which the landing container serves.
+ * self-contained HTML document served at `/offer/`. It runs server-side in the
+ * render sidecar (`renderer/src/offer.mjs`), which reads the owner-edited
+ * `ui/legal/offer_ru.md`, splices the live catalog price list into it and calls
+ * this function — one renderer shared with the browser build, kept unit-tested
+ * here (`offer.test.ts`).
  *
- * The input `markdown` is trusted repository content (the owner-edited
- * `ui/legal/offer_ru.md`), not user input, so the rendered HTML is deliberately
- * not sanitised. The page carries its own minimal light/dark styling so it needs
+ * The input `markdown` is trusted repository content plus the backend's own
+ * catalog projection, not user input, so the rendered HTML is deliberately not
+ * sanitised. The page carries its own minimal light/dark styling so it needs
  * neither the app bundle nor `app.css`.
  */
 export function renderOfferHtml(markdown: string): string {
@@ -55,11 +57,6 @@ export function renderOfferHtml(markdown: string): string {
       a {
         color: var(--accent);
       }
-      .back {
-        display: inline-block;
-        margin-bottom: 20px;
-        text-decoration: none;
-      }
       h1 {
         font-size: 1.6rem;
         text-align: center;
@@ -84,7 +81,6 @@ export function renderOfferHtml(markdown: string): string {
   </head>
   <body>
     <main>
-      <a class="back" href="/">← На главную</a>
       ${body}
     </main>
   </body>