feat: upgrade pricing admin with popular/featured selects and price input with BYN badge

Replace per-item toggles with top-level dropdown selects for popular and featured items.
Add PriceField component with inline gold BYN suffix badge.
Public Pricing component now uses dynamic popular/featured flags from data.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/types/content.ts

@@ -24,6 +24,8 @@ export interface PricingItem {
   name: string;
   price: string;
   note?: string;
+  popular?: boolean;
+  featured?: boolean;
 }
 
 export interface ScheduleClass {