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).

docs/PAYMENTS.md

@@ -82,7 +82,7 @@ leaking out to the open web) is allowed.
 | Execution context   | Spendable chip segments | Spend priority     |
 |---------------------|-------------------------|--------------------|
 | Inside VK (Android) | `vk`                    | —                  |
-| Inside VK (iOS)     | none — frozen (view only)| —                 |
+| Inside VK (iOS)     | `vk` (purchase-frozen)  | —                  |
 | Inside Telegram     | `telegram`              | —                  |
 | Web / native (Direct)| `direct` + `vk` + `telegram` | direct → vk → tg |
 
@@ -90,9 +90,11 @@ leaking out to the open web) is allowed.
   invisible-as-spendable there.
 - On the web the store has no jurisdiction, so all attached segments are spendable, drained
   by priority direct → vk → tg.
-- **VK iOS** is frozen for spending (Apple forbids spending virtual currency on digital
-  goods outside IAP inside VK on iOS): the balance is shown as a number, but no purchase or
-  spend is possible. A previously bought benefit still *applies* there.
+- **VK iOS is a PURCHASE freeze, not a spend freeze.** Apple's ToS forbids only **buying** in-app
+  values there (for any currency) — so a purchase (money → chips) is refused. **Spending** VK-wallet
+  chips (earned via rewarded ads or bought on the same VK account elsewhere, e.g. VK Android) and
+  earning them are legal and stay allowed on VK iOS; a bought benefit also *applies* there. Only the
+  money-in step is blocked.
 
 The account is **single** (identities merge, one profile/friends/stats). The gate is
 **logical**: in a VK/TG context the server activates only the same-named segment. It rests