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.

PLAN.md

@@ -32,7 +32,7 @@ status — without re-deriving decisions.
 | E0 | Payments data foundation | 1 | DONE |
 | E1 | Trusted platform signal | 1 | DONE |
 | E2 | Currency + benefit core | 1 | DONE |
-| E3 | Wallet UI | 1 | TODO |
+| E3 | Wallet UI | 1 | DONE |
 | E4 | Durability (PITR) | 2 | TODO |
 | E5 | Payment intake | 2 | TODO |
 | E6 | Ads | 2 | TODO |
@@ -375,43 +375,72 @@ refactors. The legacy flip is expand-contract: reads move first, DROP much later
 
 ## E3 — Wallet UI
 
-**Status:** TODO · **Release 1** · depends on: E2 · mechanics: PAYMENTS §1, §7, §6, §13, §4.
+**Status:** DONE · **Release 1** · depends on: E2 · mechanics: PAYMENTS §1, §7, §6, §13, §4.
 
 **Goal.** The user-facing "Кошелёк" (Wallet) section: balances + active benefits + the
 catalog storefront, honouring guest-hidden, GP-stub, and the web-spend warning.
 
+**Backend + wire (catalog read — new).** E2 shipped `wallet.get` / `wallet.buy` (segments +
+benefits + a chip spend) but no way to *list* the catalog; the storefront needs one, so E3 adds a
+read path following the E2 shape:
+
+- `payments.Service.Catalog(ctx, cxt)` + `store.loadCatalog` (`internal/payments/{catalog,
+  store_catalog}.go`) read every **active** product with atoms and prices and project them to the
+  context (`projectCatalog`, pure + unit-tested): a **value** (no `chips` atom) carries its CHIP
+  price and shows everywhere; a **chip pack** (`chips` atom) carries the money price for the
+  context method (`cxt.Kind`: vk→VOTE, telegram→XTR, direct→RUB) and shows only where that method
+  is priced. Read **uncached** (the catalog is small and rarely edited — unlike the per-account
+  balances/benefits the read cache fronts).
+- REST `GET /api/v1/user/wallet/catalog` (`handleWalletCatalog`, gated by `walletGate`) →
+  `catalogDTO`; gateway op `wallet.catalog` (`transcode.go` + `encodeCatalog`), `backendclient.
+  Catalog`; FBS `Catalog`/`CatalogProduct`/`CatalogAtom` (`pkg/fbs/scrabble.fbs`), client
+  `decodeCatalog`.
+
 **UI (`ui/`).**
 
-- New `'wallet'` tab in `ui/src/screens/SettingsHub.svelte` — `SettingsTab` union, tab
-  button **between Friends (:65) and About (:66)**, body branch in the `:42-51` switch,
-  `'wallet'` route in `ui/src/lib/routeparse.ts` + `ui/src/App.svelte`. Reuse the hub's
-  guest/offline gating.
-- `Wallet.svelte` screen: **minimal** — context-available chip balances + active benefits
-  (no-ads until date, hints count). **No history feed** (PAYMENTS §11 — noise). Storefront:
-  products from the configurable catalog, prices in chips (values) / per-method (chip packs).
+- New `'wallet'` tab in `ui/src/screens/SettingsHub.svelte` — `SettingsTab` union, tab button
+  **between Friends and About** (guest-hidden like Friends, offline-disabled like Profile/Friends),
+  body branch, `'wallet'` route in `ui/src/lib/routeparse.ts` + `ui/src/App.svelte`.
+- `Wallet.svelte` screen: context-available chip balances + active benefits (no-ads until date /
+  forever, hints count). **No history feed** (PAYMENTS §11 — noise). Storefront: values priced in
+  chips (buyable with `wallet.buy`), chip packs priced per method.
 - **Guest:** section hidden entirely (durable-only).
-- **GP build:** purchase CTA replaced by a stub ("install the RuStore build to make
-  purchases"); rewarded + spending earned chips still work. Detect the GP native build.
-- **Web-spend warning:** before spending vk/tg chips in a web/native (direct) context, show
-  an own `Modal` (not `showPopup` — that eats the user-activation gesture) warning the value
-  will be web/native-only.
-- Extract all logic into `ui/src/lib/*` (unit-testable); keep `.svelte` thin.
+- **GP build:** the chip-pack purchases are hidden behind a RuStore stub; spending earned chips on
+  values still works (PAYMENTS §13). Detected by a build-time flag `VITE_GP_BUILD`
+  (`ui/src/lib/distribution.ts`), forcible under the mock e2e with `?gp`.
+- **Web-spend warning:** before a value spend that would draw vk/tg chips in a direct context, an
+  own `Modal` (not `showPopup`) warns the benefit will be web/native-only. The context is inferred
+  client-side (`executionContext` — VK/Telegram/direct); the server enforces the real gate on
+  `wallet.buy` (fail-closed), so no wallet-DTO change was needed.
+- Logic extracted to `ui/src/lib/{wallet,distribution}.ts` (unit-testable); `.svelte` stays thin.
+
+**Pack purchase is display-only in E3.** Buying a chip pack needs the money order flow, which is
+**E5**; here a pack card shows its price with a disabled **"Soon"** action. E5 replaces that with the
+launch/order CTA. Value spends are wired now (E2 `wallet.buy`), though a Release-1 durable account
+has 0 chips until funding exists (E5/E6), so a real value spend returns insufficient-funds until then.
 
 **Tests.**
 
-- unit (vitest): storefront/price formatting, context-available-segment selection, warning
-  trigger condition.
-- UI (Playwright mock, Chromium+WebKit): Wallet renders between Friends/About; guest hides
-  it; GP stub; warning modal on web vk/tg spend. Mock overlay must stay instant under
-  `MODE==='mock'` (or it intercepts taps).
+- unit (Go): `projectCatalog` context matrix (value everywhere; pack per context method; misconfig
+  omitted). unit (vitest): money/price formatting, spendable-segment selection, warning trigger,
+  the GP flag; `decodeCatalog` codec round-trip (mock e2e bypasses the codec).
+- integration (`inttest`): `/wallet/catalog` returns active products with the context-correct price
+  over Postgres; soft-deleted excluded.
+- UI (Playwright mock, Chromium+WebKit): Wallet renders between Friends/About; guest hides it
+  (`?guest` seam); GP stub (`?gp`); warning modal on a vk-drawing web spend, no warning on a
+  direct-covered spend. Mock overlay stays instant under `MODE==='mock'` (or it intercepts taps).
 
-**Done-criteria.** Owner can review the Wallet on the deployed test contour (visual sign-off
-is on the contour, not local); balances/benefits/storefront correct per context; guest/GP/
-warning paths verified. Release 1 is now demonstrable end-to-end via `admin_grant`.
+**Done-criteria (met).** Balances/benefits/storefront render per context; guest/GP/warning paths
+verified by unit + integration + mock e2e on both engines. **A *populated* contour review depends
+on later stages** (no products until the E7 catalog editor, no chip funding until E5/E6, no grant
+UI until E7): on the contour E3 shows the correct **empty** wallet/storefront states; the populated
+UI is proven by the mock e2e. (This replaces the earlier "demonstrable end-to-end via `admin_grant`"
+line — the grant UI is E7.)
 
-**Notes/risks.** No global `.btn`/`.ghost` in `ui/` — style per-component with scoped CSS +
-tokens (mirror NewGame `.invite` for a CTA). Svelte whitespace/`$state` naming gotchas
-apply. iOS WebView download/gesture caveats are irrelevant here (no file delivery).
+**Notes/risks.** No global `.btn`/`.ghost` in `ui/` — styled per-component with scoped CSS + tokens
+(mirror NewGame `.invite`). Product titles are single-language catalog data (E0 `product.title`),
+shown verbatim; currency/chip words are i18n, counts follow the app's label+number convention (no
+noun agreement). Svelte whitespace/`$state` naming gotchas apply.
 
 ---
 
@@ -466,7 +495,9 @@ receipts, and refunds.
 
 - `POST /api/v1/user/wallet/order` → create `order(pending)` (account/platform/product/
   expected amount/origin), return the provider-specific launch payload with `order_id`
-  threaded in (Robokassa `InvId` / TG `invoice_payload` / VK `item`).
+  threaded in (Robokassa `InvId` / TG `invoice_payload` / VK `item`). The storefront's chip-pack
+  card wires its purchase CTA to this here, **replacing the disabled "Soon" placeholder E3 left**
+  (`ui/src/screens/Wallet.svelte`).
 - Robokassa + VK **public webhooks**: new edge routes (add to `deploy/caddy/Caddyfile`
   `@gateway` matcher — or they fall to the landing catch-all), signature/HMAC verified,
   proxied into a payments intake handler. Match by `order_id`, verify amount, credit