feat(ui): wire the chip-pack purchase to Robokassa

Replace the disabled "Soon" pack action with a real purchase: the Wallet opens a
money order (wallet.order) and sends the player to the provider's hosted-payment
page (window.open via openExternalUrl); the chips are credited later by the
verified server callback. Add a public-offer link under the packs (paying
accepts the offer). Codec order round-trip unit test + a mock-e2e purchase test;
the Google Play stub and the chip-spend paths are unchanged.

ui/src/lib/model.ts

@@ -172,6 +172,14 @@ export interface Wallet {
 
 /** One atom line of a storefront product: the base value type it grants ("chips"/"hints"/
  *  "noads_days"/"tournament") and how many of it the product carries. */
+// WalletOrder is a created money order to fund a chip pack: its id and the provider launch URL the
+// client opens (the Robokassa hosted-payment page). Chips arrive later, by the verified server
+// callback.
+export interface WalletOrder {
+  orderId: string;
+  redirectUrl: string;
+}
+
 export interface CatalogAtom {
   atomType: string;
   quantity: number;