Omit payment links when disabled

src/App.jsx

@@ -233,8 +233,8 @@ const TABS = [
 
 const FREE_LEVEL_IDS = new Set([1, 2, 3, 4, 8, 9, 10, 18]);
 const CORE_ARTICLE_CASES = ['nominative', 'accusative', 'dative'];
-const PAYMENTS_ENABLED = String(import.meta.env.VITE_PAYMENTS_ENABLED || 'false').toLowerCase() === 'true';
-const STRIPE_PLANS = [
+const PAYMENTS_ENABLED = import.meta.env.VITE_PAYMENTS_ENABLED === 'true';
+const STRIPE_PLANS = PAYMENTS_ENABLED ? [
   {
     id:'weekly',
     name:'Weekly',
@@ -262,7 +262,7 @@ const STRIPE_PLANS = [
     url: import.meta.env.VITE_STRIPE_LIFETIME_URL || '',
     env:'VITE_STRIPE_LIFETIME_URL',
   },
-];
+] : [];
 
 const LEVELS = [
   {id:1, tab:'article', name:'Nominativ', desc:'Gender basics: der, die, or das?', cases:['nominative'], preps:[], type:'article', artType:'definite'},