feat(admin): remove all department/campus scoping from frontend

- Delete CampusSwitcher component and useCampus hook
- Delete Departments page and its route
- Remove campus header interceptor from API client
- Remove departmentId from Class interfaces
- Remove campusLocation from student profile
- Remove department permissions from test fixtures
- Remove currentCampusId from test cleanup

TypeScript compiles clean.

apps/admin/src/components/StudentProfileContent/index.tsx

@@ -53,7 +53,6 @@ interface ProfileData {
   targetMajor?: string;
   subjectDirection?: string;
   grade?: string;
-  campusLocation?: string;
   profileDate?: string;
   notes?: string;
 }
@@ -220,7 +219,6 @@ const ProfileTab: React.FC<{ data: ProfileData | null; studentId: number; onRefr
           targetMajor: data?.targetMajor ?? undefined,
           subjectDirection: data?.subjectDirection ?? undefined,
           grade: data?.grade ?? undefined,
-          campusLocation: data?.campusLocation ?? undefined,
           profileDate: data?.profileDate ? dayjs(data.profileDate) : undefined,
           notes: data?.notes ?? undefined,
         }}
@@ -238,9 +236,6 @@ const ProfileTab: React.FC<{ data: ProfileData | null; studentId: number; onRefr
         <Form.Item name="grade" label="年级">
           <Input placeholder="如：高三" />
         </Form.Item>
-        <Form.Item name="campusLocation" label="校区">
-          <Input placeholder="请输入校区" />
-        </Form.Item>
         <Form.Item name="profileDate" label="建档日期">
           <DatePicker style={{ width: '100%' }} />
         </Form.Item>
@@ -903,9 +898,6 @@ const StudentProfileContent: React.FC<StudentProfileContentProps> = ({
         {profile?.subjectDirection && (
           <Descriptions.Item label="选科方向">{profile.subjectDirection}</Descriptions.Item>
         )}
-        {profile?.campusLocation && (
-          <Descriptions.Item label="校区">{profile.campusLocation}</Descriptions.Item>
-        )}
       </Descriptions>
 
       <Tabs