修复首屏：增加预加载占位并提前恢复主题

app/lib/useTheme.js

@@ -1,14 +1,7 @@
 /** 浅色/深色/跟随系统三态主题，使用共享 Nuxt 状态与 html.app-dark 驱动组件和原生控件。 */
 import { computed } from "vue";
 import { useState } from "#app";
-// 存储不可用或值未知时安全回落 auto，不让浏览器隐私限制阻断页面初始化。
-function n(e) {
-  try {
-    let t = (e ?? globalThis.localStorage)?.getItem(`theme`);
-    if (t === `light` || t === `dark`) return t;
-  } catch {}
-  return `auto`;
-}
+import { applyTheme } from "~/utils/theme-appearance.js";
 var r = [`light`, `dark`, `auto`],
   i = {
     light: `浅色`,
@@ -22,7 +15,7 @@ var r = [`light`, `dark`, `auto`],
   },
   o = `theme`;
 function s() {
-  let s = useState(`theme-mode`, () => n()),
+  let s = useState(`theme-mode`, () => applyTheme().mode),
     c = useState(
       `theme-dark`,
       () =>
@@ -30,17 +23,8 @@ function s() {
         document.documentElement.classList.contains(`app-dark`),
     ),
     l = () => window.matchMedia(`(prefers-color-scheme: dark)`);
-  // 仅 auto 读取系统偏好；显式 light/dark 不受系统变化影响。
-  function u() {
-    c.value = s.value === `dark` || (s.value === `auto` && l().matches);
-  }
-  function d() {
-    let e = document.documentElement;
-    (e.classList.toggle(`app-dark`, c.value),
-      (e.style.colorScheme = c.value ? `dark` : `light`));
-  }
   function f() {
-    (u(), d());
+    c.value = applyTheme(s.value).dark;
   }
   let p = null,
     m = () => {
@@ -51,7 +35,12 @@ function s() {
     (p?.removeEventListener(`change`, m), (p = null));
   }
   function g() {
-    (h(), (s.value = n()), f(), (p = l()), p.addEventListener(`change`, m));
+    h();
+    const appearance = applyTheme();
+    s.value = appearance.mode;
+    c.value = appearance.dark;
+    p = l();
+    p.addEventListener(`change`, m);
   }
   // 调用方传入已知模式；持久化失败不影响当前页面切换。
   function _(e) {