fix: Provide initial value to useRef in usePrevious hook

TypeScript requires an initial value argument when calling useRef.
Changed useRef<T>() to useRef<T | undefined>(undefined) to fix
build error and properly type the ref for the first render.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/hooks/usePrevious.ts

@@ -15,7 +15,7 @@
 import { useEffect, useRef } from "react";
 
 export function usePrevious<T>(value: T): T | undefined {
-  const ref = useRef<T>();
+  const ref = useRef<T | undefined>(undefined);
 
   useEffect(() => {
     ref.current = value;