⚡ Bolt: Prevent unnecessary AppBackground re-renders

[alazndy]

💡 What: Wrapped the AppBackground component in React.memo and assigned its displayName to ensure debugging remains clear.
🎯 Why: AppBackground sits at the top level of the widget tree inside App.tsx. Since App.tsx handles complex and frequent state updates—like drag-and-drop actions, widget reordering, clock ticks, and layout updates—the massive AppBackground (which contains images, SVGs, and potentially expensive DOM elements like glow orbs) was re-rendering unnecessarily every time an unrelated state change occurred.
📊 Impact: Reduces rendering overhead during interactive events (like dragging widgets or opening modals) by preventing the background tree from re-computing when its props (like bgConfig and activeTheme) have not changed.
🔬 Measurement: Verify by running the application in development mode with React Developer Tools' "Highlight updates when components render" enabled. Dragging widgets or waiting for the clock to tick no longer causes AppBackground to flash. Build compilation passes normally.

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PR created automatically by Jules for task 5589254451298462564 started by @alazndy

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