Dark模式 oss存储

core/frontend/src/theme.ts

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+/** 外观主题：浅色 / 深色 / 跟随系统。写到 html[data-theme] + localStorage，避免首屏闪白。 */
+
+export type Appearance = "light" | "dark" | "system";
+
+export const THEME_STORAGE_KEY = "yingqing-appearance";
+
+export function normalizeAppearance(value: unknown): Appearance {
+  if (value === "light" || value === "dark" || value === "system") return value;
+  return "system";
+}
+
+export function resolveTheme(appearance: Appearance): "light" | "dark" {
+  if (appearance === "light" || appearance === "dark") return appearance;
+  if (typeof window !== "undefined" && window.matchMedia("(prefers-color-scheme: dark)").matches) {
+    return "dark";
+  }
+  return "light";
+}
+
+export function applyTheme(appearance: Appearance | string | null | undefined) {
+  if (typeof document === "undefined") return;
+  const normalized = normalizeAppearance(appearance);
+  const theme = resolveTheme(normalized);
+  const root = document.documentElement;
+  root.setAttribute("data-theme", theme);
+  root.style.colorScheme = theme;
+  try {
+    localStorage.setItem(THEME_STORAGE_KEY, normalized);
+  } catch {
+    /* ignore quota / private mode */
+  }
+}
+
+export function readStoredAppearance(): Appearance {
+  try {
+    return normalizeAppearance(localStorage.getItem(THEME_STORAGE_KEY));
+  } catch {
+    return "system";
+  }
+}