refactor(代码重复): 抽取共享工具函数与 UI 组件，消除多处重复实现

Co-authored-by: Cursor <cursoragent@cursor.com>

src/utils/syncSnapshot.ts

@@ -0,0 +1,21 @@
+/**
+ * 从 localStorage 获取同步快照（用于消除异步加载产生的首屏闪烁）
+ */
+export function getSyncSnapshot<T>(
+  key: string,
+  defaultValue: T,
+  validator?: (val: unknown) => val is T,
+): T {
+  try {
+    const val = localStorage.getItem(`snapshot/${key}`);
+    if (!val) return defaultValue;
+    const parsed = JSON.parse(val) as unknown;
+    if (validator) {
+      return validator(parsed) ? parsed : defaultValue;
+    }
+    return (parsed as T) ?? defaultValue;
+  } catch (error) {
+    console.error(`[SyncSnapshot] Failed to read snapshot/${key}:`, error);
+    return defaultValue;
+  }
+}