fix(payment-methods): admin display_name/description override locale on balance

White-label (per-method display_name + description in admin) was defeated on
balance/top-up pages: render used `translatedName || method.name` and
`translatedDesc || method.description`, so the bundled locale always won and
the admin override was ignored.

- Flip priority: admin-configured value first, locale as fallback
  (TopUpMethodSelect, Balance)
- Add missing Description field to payment-method edit page
  (mirrors Display name: description / reset_description)
- Add description to admin PaymentMethodConfig type
- Add description/descriptionHint i18n keys (ru, en)

src/types/index.ts

@@ -689,6 +689,7 @@ export interface PaymentMethodConfig {
   is_enabled: boolean;
   display_name: string | null;
   default_display_name: string;
+  description: string | null;
   sub_options: Record<string, boolean> | null;
   available_sub_options: PaymentMethodSubOptionInfo[] | null;
   quick_amounts: number[] | null;