React 19: useRef<T>() -> useRef<T>(null) across 15 sites

React 19 dropped the no-arg useRef overload — the type-only useRef<T>()
form (no initial value) is gone, every call must pass an initial value.
The codebase had 15 occurrences of useRef<HTMLDivElement>() (DOM ref
pattern) all flagged by tsgo as 'Expected 1 arguments, but got 0'.

Mechanical sweep to useRef<HTMLDivElement>(null) — no behavior change,
React still hands out a ref object with .current set to null at mount.

Net tsgo error count: 57 -> 42.

src/components/game-center/views/GameStageView.tsx

@@ -7,7 +7,7 @@ export const GameStageView = () =>
 {
     const { gameURL, setGameURL } = useGameCenter();
     const [ loadTimes, setLoadTimes ] = useState<number>(0);
-    const ref = useRef<HTMLDivElement>();
+    const ref = useRef<HTMLDivElement>(null);
 
     useEffect(() =>
     {