Best practice-ek

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# Conventions
We try to write good code.

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# Naming Conventions
- Components: PascalCase, feature-prefix (ProductCard, UserAvatar)
- Hooks: camelCase, use-prefix (useProductList, useCartTotal)
- Store actions: verb-noun (setUser, clearCart, updateQuantity)

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Always use server components.

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Default to Server Components (no "use client" directive).
Add "use client" only when you need: event handlers, useState,
useEffect, or browser-only APIs. This improves performance by
reducing the client-side JavaScript bundle.

Create TypeScript interfaces for the User and Order entities.
Format: one interface per file in src/types/, with JSDoc comments
for each field, and export from src/types/index.ts.

@src/components/ProductCard.tsx

Create a similar OrderCard component for the orders list.
Follow the same structure, prop types pattern, and styling approach.

# 1. lépés
Create the Zustand store for the shopping cart with
add, remove, and update quantity actions.

# 2. lépés (ha az előző kész és tesztelt)
@src/store/cartStore.ts
Add a derived selector that calculates the total price
including discounts and taxes.