Function useGameVisibility

useGameVisibility(game: Game): UseGameVisibilityResult
Manages question-visibility state for the GM view.
Parameters
- game: Game
  The active game. Initial visibility values are read from this record.
Returns UseGameVisibilityResult
Remarks
The GM can independently reveal the question text, answer options, and associated media to players. Each toggle is persisted to the games table and broadcast via the VISIBILITY transport event so all connected players update immediately.

Optimistic updates are applied locally before the DB write completes. If the write fails, the previous state is restored and error is set.
Example
```
function VisibilityPanel({ game }: { game: Game }) {
  const { visibility, toggle, saving } = useGameVisibility(game)
  return (
    <button onClick={() => toggle('showQuestion')} disabled={saving}>
      {visibility.showQuestion ? 'Hide' : 'Show'} Question
    </button>
  )
}
```
- Defined in src/hooks/useGameVisibility.ts:55