fix: render the trailing switch on iOS list items

[SRWieZ]

The bug

Give a list item a trailing switch:

<native:list-item headline="Keep screen awake"
    :trailingSwitch="$keepAwake" on-trailing-change="setKeepAwake" />

On Android you get a Material Switch. On iOS you get nothing — the row renders with an empty trailing slot, no error anywhere.

Why

In NativeUIListItemRenderer.swift, the trailing switch case was a stub:

case "switch":
    EmptyView() // Switch requires state management - handled at a higher level

There is no "higher level" — nothing else ever renders it.

The fix

Render a real SwiftUI Toggle, following the exact pattern NativeUIToggleRenderer already uses:

• Local @State, so the thumb animates instantly on tap.
• Echo prevention: a server re-render that just echoes the value we sent doesn't snap the thumb back, but a genuine programmatic change still updates it.
• Tinted with the theme's primary color, like every other switch.
• Reports the new value (a bool) through the row's on_trailing_change callback — the same payload Android has always sent, so one PHP handler works on both platforms.
• A disabled row, or one without a callback, shows a non-interactive switch.

No Android changes, no PHP changes, no API changes — trailingSwitch() simply starts working on iOS.