fix: resolve all 14 ESLint warnings across the codebase

- Add varsIgnorePattern to no-unused-vars for destructuring patterns
- Fix all react-hooks/exhaustive-deps by adding missing dependencies
- Refactor useAnimatedNumber to use ref instead of stale state closure
- Wrap handleLinkResult in useCallback for stable deps
- Extract OAuth utilities from OAuthCallback.tsx to utils/oauth.ts
- Extract background config utilities to utils/backgroundConfig.ts
- Remove unused catch parameter in GiftSubscription

src/hooks/useAnimatedNumber.ts

@@ -6,20 +6,19 @@ import { useEffect, useRef, useState } from 'react';
  */
 export function useAnimatedNumber(target: number, duration = 1200): number {
   const [value, setValue] = useState(0);
-  const ref = useRef({ start: 0, startTime: 0, target: 0 });
+  const currentRef = useRef(0);
   const rafRef = useRef<number>(0);
 
   useEffect(() => {
-    ref.current.start = value;
-    ref.current.target = target;
-    ref.current.startTime = performance.now();
+    const start = currentRef.current;
+    const startTime = performance.now();
 
     const animate = (now: number) => {
-      const elapsed = now - ref.current.startTime;
+      const elapsed = now - startTime;
       const progress = Math.min(elapsed / duration, 1);
-      // easeOutExpo
       const ease = progress === 1 ? 1 : 1 - Math.pow(2, -10 * progress);
-      const current = ref.current.start + (ref.current.target - ref.current.start) * ease;
+      const current = start + (target - start) * ease;
+      currentRef.current = current;
       setValue(current);
       if (progress < 1) {
         rafRef.current = requestAnimationFrame(animate);