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.

ui/src/lib/transport.ts

@@ -228,6 +228,16 @@ export function createTransport(baseUrl: string): GatewayClient {
       return codec.decodeFeedbackUnread(await exec('feedback.unread', codec.empty()));
     },
 
+    async wallet() {
+      return codec.decodeWallet(await exec('wallet.get', codec.empty()));
+    },
+    async catalog() {
+      return codec.decodeCatalog(await exec('wallet.catalog', codec.empty()));
+    },
+    async walletBuy(productId: string) {
+      return codec.decodeWallet(await exec('wallet.buy', codec.encodeWalletBuy(productId)));
+    },
+
     async friendsList() {
       return codec.decodeFriendList(await exec('friends.list', codec.empty()));
     },