fix(frontend): resolve all eslint errors to zero (B1)

frontend/src/readers/CbzReader.tsx

@@ -38,10 +38,17 @@ function PageImg({ url, width, onLoaded }: { url: string; width: number; onLoade
   const [src, setSrc] = useState("");
   const [failed, setFailed] = useState(false);
   const [nonce, setNonce] = useState(0);
-  useEffect(() => {
-    let dead = false;
+  // url/nonce 变化时先落回占位态:React 官方推荐的「渲染期按下发 key 重置本地 state」,
+  // 替代原先 effect 内的同步 setState(级联渲染);换页/重试时的表现与原先一致
+  const key = url + "#" + nonce;
+  const [prevKey, setPrevKey] = useState(key);
+  if (prevKey !== key) {
+    setPrevKey(key);
     setSrc("");
     setFailed(false);
+  }
+  useEffect(() => {
+    let dead = false;
     fetchObjectUrl(url)
       .then((s) => !dead && setSrc(s))
       .catch(() => !dead && setFailed(true));