feat(android): resolve gateway origin on native, skip SW, hide MVP purchases

Make the web SPA behave correctly inside the Capacitor native shell, where the
bundle loads from a local origin:

- New lib/origin.ts gatewayOrigin(): absolute URLs resolve to VITE_GATEWAY_URL on
  native (the finished-game export/share URL in Game.svelte and the Wallet
  site-root link), falling back to the page origin on web. transport.ts already
  resolved via VITE_GATEWAY_URL and is left as-is.
- Skip the PWA service worker on the native channel (the assets are already local;
  a worker would risk serving stale content across store updates).
- Hide the money-purchase UI in the MVP: new distribution.purchasesHidden() folds
  VITE_PAYMENTS_DISABLED and the Google Play flag. The Wallet "buy" tab shows a
  neutral, pointer-free note (wallet.purchasesSoon) for the RuStore MVP and keeps
  the RuStore stub Google-Play-only. A ?nopay mock force mirrors ?gp for the e2e.
- Native env types in vite-env.d.ts.

Client-only, contour-safe: no wire/proto/schema change; web/VK/Telegram unchanged.
Tests: origin + purchasesHidden unit tests, a ?nopay wallet e2e. svelte-check
clean, vitest green, web + native vite build clean.

ui/src/screens/Wallet.svelte

@@ -6,8 +6,9 @@
   import { normalizeSubtype } from '../lib/platform';
   import { t, i18n, type MessageKey } from '../lib/i18n/index.svelte';
   import { executionContext, formatAmount, needsWebSpendWarning, spendableChips, type SpendContext } from '../lib/wallet';
-  import { isGooglePlayBuild } from '../lib/distribution';
+  import { isGooglePlayBuild, purchasesHidden } from '../lib/distribution';
   import { onExternalLinkClick, openExternalUrl } from '../lib/links';
+  import { gatewayOrigin } from '../lib/origin';
   import { vkPlatform, vkShowOrderBox } from '../lib/vk';
   import { telegramOpenInvoice } from '../lib/telegram';
   import { rewardedReady, showRewarded } from '../lib/ads';
@@ -16,8 +17,9 @@
 
   // The Wallet section: a compact chip balance, the active benefits, and the storefront. The store
   // splits into "buy chips" (chip packs, funded with money — a provider redirect) and "spend chips"
-  // (values bought with chips — an instant exchange). On the Google Play build the money purchases
-  // are hidden behind a RuStore stub (store policy), while spending already-earned chips still works.
+  // (values bought with chips — an instant exchange). When purchases are hidden — the Google Play
+  // build (behind a RuStore stub, store policy) or the native MVP that defers billing (a neutral
+  // note) — the money purchases disappear while spending already-earned chips still works.
 
   let wallet = $state<Wallet | null>(null);
   let catalog = $state<Catalog | null>(null);
@@ -38,13 +40,16 @@
   );
 
   const gpBuild = isGooglePlayBuild();
+  // Money purchases are hidden in the Google Play build (policy) and in the native MVP that defers
+  // billing; the RuStore-pointer stub shows only for the former (gpBuild).
+  const noPurchases = purchasesHidden();
   // Money purchases are not permitted inside the VK iOS app (Apple ToS); the pack CTA is shown
   // muted and taps explain why, rather than hiding the storefront. VK's device family is not on the
   // client platformSubtype (server-derived) — read it from the signed vk_platform launch param.
   const purchaseBlocked = context === 'vk' && normalizeSubtype(vkPlatform()) === 'ios';
   // The "other version" link points at this deployment's own site root (the landing lists every
   // platform), so it follows prod vs the contour without a hardcoded host.
-  const siteRoot = typeof location !== 'undefined' ? `${location.origin}/` : '/';
+  const siteRoot = `${gatewayOrigin()}/`;
 
   const values = $derived(catalog?.products.filter((p) => p.kind === 'value') ?? []);
   const packs = $derived(catalog?.products.filter((p) => p.kind === 'pack') ?? []);
@@ -237,8 +242,12 @@
           >
         </div>
       {/if}
-      {#if gpBuild}
-        <p class="stub" data-testid="gp-stub">{t('wallet.gpStub')}</p>
+      {#if noPurchases}
+        {#if gpBuild}
+          <p class="stub" data-testid="gp-stub">{t('wallet.gpStub')}</p>
+        {:else}
+          <p class="stub" data-testid="purchases-hidden">{t('wallet.purchasesSoon')}</p>
+        {/if}
       {:else}
         {#each packs as p (p.productId)}
           <div class="row product" data-testid="product" data-kind="pack" data-pid={p.productId}>