fix: use standard purchase copy in demo

frontend/src/lib/webapp/demoDataset.js

@@ -1,3 +1,8 @@
+const DEFAULT_SUBSCRIPTION_PURCHASE_DESCRIPTION_RU =
+  "Покупая или продлевая подписку, вы получаете доступ к VPN/прокси-сервису, который помогает защищать ваше соединение и поддерживать стабильный доступ к сети.";
+const DEFAULT_SUBSCRIPTION_PURCHASE_DESCRIPTION_EN =
+  "By buying or renewing a subscription, you get access to a VPN/proxy service that helps protect your connection and keep your access stable.";
+
 export const DEMO_DATASET = {
   generatedFrom: {
     source: "tmp/postgres.dump",
@@ -96,8 +101,7 @@ export const DEMO_DATASET = {
     trial_duration_days: 5,
     trial_traffic_limit_gb: 10,
     trial_traffic_strategy: "NO_RESET",
-    subscription_purchase_description:
-      "Demo purchase copy: renewals and tariff changes use mock payments and anonymized production-like data.",
+    subscription_purchase_description: DEFAULT_SUBSCRIPTION_PURCHASE_DESCRIPTION_RU,
     subscription_guides_enabled: true,
     email_auth_enabled: true,
   },
@@ -86648,7 +86652,7 @@ export const DEMO_DATASET = {
           placeholder: "",
           optional: true,
           secret: false,
-          value: "Demo subscription_purchase_description_ru",
+          value: DEFAULT_SUBSCRIPTION_PURCHASE_DESCRIPTION_RU,
           overridden: false,
           updated_at: null,
         },
@@ -86668,7 +86672,7 @@ export const DEMO_DATASET = {
           placeholder: "",
           optional: true,
           secret: false,
-          value: "Demo subscription_purchase_description_en",
+          value: DEFAULT_SUBSCRIPTION_PURCHASE_DESCRIPTION_EN,
           overridden: false,
           updated_at: null,
         },