feat(payments): live payment-availability kill switch + per-account override

Let an operator disable purchases live from the admin — a whole rail/channel or
one account — and show the user a localized reason on their next attempt, so a
provider outage or a misconfig is explained instead of a silent dead button.

- rail kill switch (payments.rail_status, per rail direct:web / direct:android /
  vk / telegram): enabled + a per-language message, edited on the catalog page.
  Fail-open — a rail with no row stays enabled, so payments are never accidentally
  killed. The intake gate (CanPurchase in handleWalletOrder, before the order)
  returns payment_unavailable + the localized message, orthogonal to the security
  gates.
- per-account override (payments.account_payment_override, a row only for
  non-default): allow / deny / default, edited on the user card. "allow" bypasses
  ONLY the ops rail switch, never the security gates (trusted platform, the email
  anchor, the VK-iOS freeze, the min client version).
- wire: an additive ExecuteResponse.message envelope field (frozen-contract-safe);
  the gateway forwards a backend domain-error message; the client shows it on a
  payment_unavailable buy attempt.
- admin: rail toggles on the catalog page, the override control on the user card.
- tests: the pure gate (unit, TDD), the store + gate + override end-to-end
  (integration, migration 00016), the client (svelte-check / vitest).
- docs: PAYMENTS (+ru), the decisions log (D45/D46). Fiscalization stays
  cabinet-side (owner decision) — no itemized-receipt code.

Contour-safe: additive migration (two new tables, no wipe), the wire add is
additive, and fail-open so nothing is disabled until an operator acts.

PLAN.md

@@ -39,7 +39,8 @@ status — without re-deriving decisions.
 | E7 | Admin, reports & catalog | 2 | DONE |
 | E8 | Guest limits | — | DONE |
 | E9 | Tournament fee | future | TODO |
-| E10 | Multi-shop direct rail + ИП fiscalization | 2+ | TODO |
+| E10 | Multi-shop direct rail + ИП fiscalization | 2+ | DONE |
+| E11 | Payment availability kill switch + per-account override | 2 | DONE |
 
 **Release 1** = full mechanics with no real money, exercised via `admin_grant` (E0→E1→E2→E3).
 **Release 2** = money (E4→E5→E6→E7). E8 is standalone (game-behaviour change, can run in
@@ -896,7 +897,7 @@ tournament-entry storage + pricing design.
 
 ## E10 — Multi-shop direct rail + ИП fiscalization
 
-**Status:** TODO · **Release 2+ (post-launch, backend-first)** · depends on: E5 (intake/`Fund`,
+**Status:** DONE (merged — the multi-shop PR) · **Release 2+ (post-launch, backend-first)** · depends on: E5 (intake/`Fund`,
 the `robokassa` adapter, the Result callback), E7 (the per-user report — channel breakdown) ·
 mechanics: PAYMENTS §9, §12; decisions D41 (rev), D42–D44.
 
@@ -940,7 +941,9 @@ by the **trusted** `X-Platform` subtype, never a client field; unknown → `web`
 - Keep the legacy single route alive (shop = `web`) through the expand-contract window until the
   cabinet Result URLs are cut over.
 
-**B4 — ИП fiscalization (D41 rev) — orthogonal, gated on the owner's ИП/ОФД/СНО.**
+**B4 — ИП fiscalization (D41 rev) — RESOLVED (owner 2026-07-14): cabinet-side only.** The owner keeps
+Robokassa's cabinet auto-fiscalization (a generic чек is acceptable for the ИП); the optional
+itemized-`Receipt` / `Email` code below is **dropped** — not needed. (Kept for context.)
 
 - **Owner/cabinet:** enable the 54-ФЗ cloud kassa in the Robokassa ЛКК (kassa + ОФД + СНО).
   Required for ИП regardless of code.
@@ -980,6 +983,35 @@ emits `direct/android` for the native build before relying on subtype routing.
 
 ---
 
+## E11 — Payment availability kill switch + per-account override
+
+**Status:** DONE · **Release 2** · depends on: E5 (intake/order), E7 (admin console) · mechanics:
+PAYMENTS §9; decisions D45, D46.
+
+**Delivered.** An operator disables purchases live from `/_gm` — a whole rail/channel or one account
+— and the user sees a localized reason on the next purchase attempt. Motivation (owner): real apps
+show broken payments with no explanation; this gives ops a live switch + a clear user message.
+
+- **Rail kill switch** — `payments.rail_status` (per rail `direct:web` / `direct:android` / `vk` /
+  `telegram`): `enabled` + a per-language message, edited on the catalog page. **Fail-open** (no row
+  ⇒ enabled, so payments are never accidentally killed). The intake gate — `CanPurchase` in
+  `handleWalletOrder`, before the order — returns `payment_unavailable` + the localized message;
+  orthogonal to the security gates.
+- **Per-account override** — `payments.account_payment_override` (a row only for non-default; default
+  = no row, cleared by delete): allow / deny / default, edited on the user card. `allow` bypasses
+  **only** the ops rail switch, never the security gates (D46).
+- **Wire** — the message rides an additive `ExecuteResponse.message` (envelope layer,
+  frozen-contract-safe; the gateway forwards a backend domain-error message via `DomainMessage`); the
+  client reads it into `GatewayError.message` and shows it on a `payment_unavailable` buy attempt.
+- **Tests** — the pure gate `PurchaseGate` (unit, TDD); the store + gate + override end-to-end
+  (integration, migration `00016`); the client (svelte-check / vitest). **Docs** — PAYMENTS (+`_ru`),
+  decisions D45 / D46.
+
+**Contour-safe:** additive migration (two new tables, no wipe); the wire add is additive; fail-open,
+so nothing is disabled until an operator acts.
+
+---
+
 ## Verification & CI (all stages)
 
 - Per-stage tests at the layers above; **compliance-gate regression is mandatory** (a