fix(payments): VK-iOS freeze is purchase-only; remove the rewarded diagnostic

Testing the rewarded slice surfaced a contradiction: rewarded ads let a VK-iOS
user earn vk chips, but the blanket VK-iOS "spend freeze" then blocked spending
them (the wallet showed "5 (view-only)"). Apple's ToS forbids only BUYING in-app
values on VK-iOS (money -> chips), not spending or earning them — so the freeze is
corrected to purchase-only: vkFrozen() now gates only CreateOrder (the money-in
step), not spendableSources (spending). VK-wallet chips — earned via rewarded ads
or bought on the same account elsewhere (VK Android) — now spend on VK-iOS too.
(Owner's ToS finding.)

Also: the temporary contour diagnostic confirmed VK returns only {result:true} for
a rewarded view (no token/signature) — client-attested is final, no hardening
possible — so the diagnostic (the log and the diag wire field) is removed.

Docs: PAYMENTS(+ru) VK-iOS freeze + D17 amend + PLAN E6. Tests updated (gate /
wallet VK-iOS now spendable).

ui/src/lib/vk.ts

@@ -213,16 +213,15 @@ export async function vkRewardedReady(): Promise<boolean> {
 
 /**
  * vkShowRewarded shows a rewarded ad (VKWebAppShowNativeAds) and reports whether it was watched
- * (data.result) plus the full raw provider result as JSON — forwarded to the backend for the
- * temporary contour diagnostic (to confirm exactly what VK returns). A rejected call reports
- * not-watched with the error captured.
+ * (data.result — VK returns only this boolean, no server-verifiable token). A rejected call reports
+ * not-watched.
  */
-export async function vkShowRewarded(): Promise<{ watched: boolean; data: string }> {
+export async function vkShowRewarded(): Promise<boolean> {
   try {
     const data = await (await bridge()).send('VKWebAppShowNativeAds', { ad_format: 'reward' });
-    return { watched: !!(data as { result?: boolean }).result, data: JSON.stringify(data) };
-  } catch (e) {
-    return { watched: false, data: JSON.stringify({ error: String(e) }) };
+    return !!(data as { result?: boolean }).result;
+  } catch {
+    return false;
   }
 }