refactor(web): 前端目录重构 — consoles/pages → layouts/features + shared

- consoles/admin/ → layouts/admin-layout/
- consoles/workbench/ → layouts/workbench-layout/ + features/chat/
- pages/ → features/ (dashboard, models, projects, not-found)
- components/ → shared/components/
- hooks/ → shared/hooks/
- utils/ → shared/utils/
- 更新所有 import 路径 (src/web/ + tests/web/)
- 更新开发文档 (README.md, frontend.md, architecture.md)

src/web/shared/hooks/use-theme-preference.ts

@@ -0,0 +1,61 @@
+import { useEffect, useState } from "react";
+
+export type EffectiveTheme = "dark" | "light";
+export type ThemePreference = "dark" | "light" | "system";
+
+export const THEME_PREFERENCE_STORAGE_KEY = "theme.preference";
+export const THEME_MEDIA_QUERY = "(prefers-color-scheme: dark)";
+
+export function getSystemPrefersDark(matchMedia: Window["matchMedia"] = window.matchMedia): boolean {
+  try {
+    return matchMedia(THEME_MEDIA_QUERY).matches;
+  } catch {
+    return false;
+  }
+}
+
+export function parseThemePreference(value: unknown): ThemePreference {
+  return value === "dark" || value === "light" || value === "system" ? value : "system";
+}
+
+export function readThemePreference(storage: Storage = window.localStorage): ThemePreference {
+  try {
+    return parseThemePreference(storage.getItem(THEME_PREFERENCE_STORAGE_KEY));
+  } catch {
+    return "system";
+  }
+}
+
+export function resolveEffectiveTheme(preference: ThemePreference, systemPrefersDark: boolean): EffectiveTheme {
+  if (preference === "dark" || preference === "light") return preference;
+  return systemPrefersDark ? "dark" : "light";
+}
+
+export function useThemePreference() {
+  const [preference, setPreferenceState] = useState<ThemePreference>(() => readThemePreference());
+  const [systemPrefersDark, setSystemPrefersDark] = useState(() => getSystemPrefersDark());
+  const effectiveTheme = resolveEffectiveTheme(preference, systemPrefersDark);
+
+  useEffect(() => {
+    const mediaQueryList = window.matchMedia(THEME_MEDIA_QUERY);
+
+    const handleChange = (event: MediaQueryListEvent) => setSystemPrefersDark(event.matches);
+    mediaQueryList.addEventListener("change", handleChange);
+    return () => mediaQueryList.removeEventListener("change", handleChange);
+  }, []);
+
+  const setPreference = (nextPreference: ThemePreference) => {
+    setPreferenceState(nextPreference);
+    writeThemePreference(nextPreference);
+  };
+
+  return { effectiveTheme, preference, setPreference };
+}
+
+export function writeThemePreference(preference: ThemePreference, storage: Storage = window.localStorage) {
+  try {
+    storage.setItem(THEME_PREFERENCE_STORAGE_KEY, preference);
+  } catch {
+    // 存储不可用时仅使用当前内存状态，避免阻断 Dashboard 渲染。
+  }
+}