feat(payments): wallet screen with balances, benefits and storefront

Add the "Кошелёк" section to the settings hub: context-visible chip
balances, active benefits (no-ads term/forever, hints) and a storefront of
chip-priced values and money-priced chip packs. Guests have no wallet; the
Google Play build hides the money purchases behind a RuStore stub; a web
purchase that would draw VK/Telegram chips warns first.

Add the catalog read path the storefront needs — a context-projected
GET /api/v1/user/wallet/catalog (payments service + store, gateway op
wallet.catalog, FBS Catalog/CatalogProduct/CatalogAtom, client decode) —
plus the client leg for the existing wallet.get/buy ops. Value spends reuse
the existing spend path; the chip-pack purchase (money order flow) arrives
with payment intake, so its action is a disabled placeholder for now.

Covered by Go unit (catalog projection) + integration (/wallet/catalog over
Postgres), vitest (formatting, spendable selection, web-spend warning, GP
flag, codec + gateway encode round-trips) and Playwright mock e2e (render,
guest-hidden, GP stub, warning) on Chromium + WebKit.

docs/FUNCTIONAL.md

@@ -522,6 +522,25 @@ stops only feedback submission). Roles are listed and granted/revoked on the use
 message does not mark it read — only the explicit actions do; message bodies and attachments are
 shown defensively (text escaped, attachments downloaded rather than rendered).
 
+### Wallet
+
+Durable players have a **Wallet** — a tab in the Settings hub, between Friends and About; guests have
+none. It shows their **chips** (the in-game currency, split by where they were funded — VK, Telegram
+or the web), their **active benefits** (ads off until a date or forever, and the available hint
+count), and a **store**. What is visible and spendable depends on **where the app runs**, by the
+store-compliance rules in [`PAYMENTS.md`](PAYMENTS.md): inside a store only that store's chips are
+usable; on the open web all attached chips are, drawn web → VK → Telegram; on VK-iOS the balance is
+shown but frozen for spending.
+
+The **store** lists **values** bought with chips (extra hints, days without ads) at a fixed chip
+price shown in every context, and **chip packs** bought with real money, priced in the running
+context's currency (VK Votes, Telegram Stars, or roubles on the web). Buying a value applies its
+benefit at once. Before a web purchase that would draw VK/Telegram chips, the app **warns** that the
+benefit will then work only on the web and in the app — a store rule — and asks the player to confirm.
+On the **Google Play** build the money purchases are hidden behind a note pointing to the RuStore
+build (Google's in-app-currency rule); spending already-earned chips still works. The wallet keeps
+**no purchase history** — only the current balances, benefits and store.
+
 ### Advertising banner
 
 A one-line banner under the nav shows short promotional or operational messages to **free