ie-js: implement proper async setTimeout/setInterval with event loop

[thomasnemer]

Goal

setTimeout currently executes callbacks immediately (no delay). setInterval is a no-op stub. Need a proper event loop integration.

Current state

• setTimeout fires callback synchronously during script execution
• setInterval returns a dummy ID but never fires
• No event loop — scripts run to completion then rendering happens

Implementation needed

• Timer queue with scheduled callbacks
• Integration with winit event loop (or separate JS tick)
• Proper delay handling via tokio or std timers
• clearTimeout/clearInterval actually cancel pending timers
• requestAnimationFrame callback before each paint

Impact

Any site using setTimeout for deferred work or animations will behave incorrectly.