fix: eliminate home screen lag via memoization and FlashList migration

[Copilot]

The home screen was lagging due to unnecessary re-renders driven by unstable prop references and React Native's default FlatList rendering overhead.

Root causes & fixes

• contentContainerStyle new array reference every render — stabilized with useMemo so FlashList receives a stable reference.
• productFeedback calling 4 render functions unconditionally — now wrapped in useMemo, only re-evaluated when the underlying useCallback references change.
• Replaced FlatList with FlashList — migrated the product grid to @shopify/flash-list for significantly better scroll performance via its internal recycling architecture.

// Before
import { FlatList } from 'react-native';
<FlatList<Product>
  removeClippedSubviews
  columnWrapperStyle={flatListColumnWrapperStyle}
  contentContainerStyle={flatListContentContainerStyle}
  initialNumToRender={6}
  maxToRenderPerBatch={4}
  windowSize={5}
  ...
/>

// After
import { FlashList } from '@shopify/flash-list';
<FlashList<Product>
  contentContainerStyle={flashListContentContainerStyle}
  estimatedItemSize={scale(300)}
  numColumns={2}
  ...
/>

FlashList migration

Aspect	FlatList	FlashList
Rendering	Window-based	Recycling (no blank cells)
estimatedItemSize	N/A	scale(300) — device-adaptive ProductCard height estimate
columnWrapperStyle	Required for column spacing	Not needed (handled internally)
removeClippedSubviews, windowSize, maxToRenderPerBatch, initialNumToRender	Manual tuning required	Handled internally by FlashList

estimatedItemSize uses the project's scale() utility so the estimate adapts to the current device's screen dimensions.

[prince-d-simform]

@copilot can you please use the Flashlist instead of flatlist

[Copilot]

Pull request overview

This PR targets Home screen performance by reducing unnecessary re-renders and layout work in the product grid, primarily by stabilizing prop references passed to FlatList and tuning initial/batch rendering behavior.

Changes:

• Memoizes productFeedback evaluation so the feedback element is only recomputed when the underlying render callbacks change.
• Stabilizes FlatList contentContainerStyle and columnWrapperStyle references via useMemo to avoid triggering redundant work each render.
• Tunes FlatList rendering with initialNumToRender={6} and maxToRenderPerBatch={4} to reduce initial and scroll-time JS thread pressure.

[Copilot]

@copilot can you please use the Flashlist instead of flatlist

Done in f543424. Replaced FlatList with FlashList from @shopify/flash-list (v2.3.1).

Key changes:

• Added @shopify/flash-list to package.json
• Swapped FlatList → FlashList with estimatedItemSize={scale(300)} (required by FlashList, adapted to device size via the project's scale() utility)
• Removed FlatList-only props that FlashList doesn't need: columnWrapperStyle, removeClippedSubviews, windowSize, maxToRenderPerBatch, initialNumToRender — FlashList handles these optimizations internally
• Removed the now-unused columnWrapper style from HomeStyles.ts