feat: add useCampus hook and CampusSwitcher component

apps/admin/src/components/CampusSwitcher.tsx

@@ -0,0 +1,36 @@
+import React from 'react';
+import { Select, Typography } from 'antd';
+import { EnvironmentOutlined } from '@ant-design/icons';
+import { useCampus } from '../hooks/useCampus';
+
+const CampusSwitcher: React.FC = () => {
+  const { campuses, currentId, switchCampus, loading } = useCampus();
+
+  if (campuses.length <= 1) {
+    return (
+      <Typography.Text style={{ color: '#fff', marginRight: 24 }}>
+        <EnvironmentOutlined style={{ marginRight: 4 }} />
+        {campuses[0]?.name || '主校区'}
+      </Typography.Text>
+    );
+  }
+
+  const options = [
+    ...campuses.map((c) => ({ value: String(c.id), label: c.name })),
+    { value: '', label: '全部校区' },
+  ];
+
+  return (
+    <Select
+      value={currentId || undefined}
+      onChange={switchCampus}
+      options={options}
+      loading={loading}
+      style={{ minWidth: 140, marginRight: 24 }}
+      variant="borderless"
+      popupMatchSelectWidth={false}
+    />
+  );
+};
+
+export default CampusSwitcher;

apps/admin/src/hooks/useCampus.ts

@@ -0,0 +1,40 @@
+import { useState, useEffect, useCallback } from 'react';
+import api from '../api';
+
+interface Department {
+  id: number;
+  name: string;
+  type: string;
+  parentId: number | null;
+}
+
+export function useCampus() {
+  const [campuses, setCampuses] = useState<Department[]>([]);
+  const [currentId, setCurrentId] = useState<string>(
+    () => localStorage.getItem('currentCampusId') || ''
+  );
+  const [loading, setLoading] = useState(true);
+
+  const fetchCampuses = useCallback(async () => {
+    try {
+      const data = await api.get('/departments') as unknown as Department[];
+      const campusList = data.filter((d) => d.type === 'campus');
+      setCampuses(campusList);
+      if (!currentId && campusList.length > 0) {
+        setCurrentId(String(campusList[0].id));
+        localStorage.setItem('currentCampusId', String(campusList[0].id));
+      }
+    } catch { /* ignore */ }
+    finally { setLoading(false); }
+  }, [currentId]);
+
+  useEffect(() => { fetchCampuses(); }, []);
+
+  const switchCampus = useCallback((id: string) => {
+    setCurrentId(id);
+    localStorage.setItem('currentCampusId', id);
+    window.dispatchEvent(new CustomEvent('campus-changed', { detail: id }));
+  }, []);
+
+  return { campuses, currentId, switchCampus, loading };
+}