fix: include contained room expenses in bill generation

apps/server/src/bills/bills.service.spec.ts

@@ -166,6 +166,43 @@ describe('BillsService — generateBills', () => {
     ).toBeCloseTo(300, 0);
   });
 
+  it('includes room expenses whose periods are inside the generated bill period', async () => {
+    const qb = mockQueryBuilder<RoomExpense>([
+      {
+        id: 1, roomId: 1, expenseType: 'water',
+        amount: '300' as unknown as number, periodStart: '2026-07-01', periodEnd: '2026-07-31',
+      } as RoomExpense,
+    ]);
+    (roomExpRepo.createQueryBuilder as jest.Mock).mockReturnValue(qb);
+
+    (occRepo.createQueryBuilder as jest.Mock).mockReturnValue(
+      mockQueryBuilder<Occupancy>([
+        {
+          id: 1, studentId: 10, roomId: 1,
+          billingStartDate: '2026-07-01', billingEndDate: null as unknown as string,
+          stayType: 'short', room: undefined,
+        } as Occupancy,
+      ]),
+    );
+
+    (personalExpRepo.createQueryBuilder as jest.Mock).mockReturnValue(
+      mockQueryBuilder<PersonalExpense>([]),
+    );
+
+    const result = await service.generateBills({
+      periodStart: '2026-06-29',
+      periodEnd: '2026-07-31',
+    });
+
+    expect(result.count).toBe(1);
+    expect(qb.where).toHaveBeenCalledWith(
+      'e.periodStart >= :periodStart AND e.periodEnd <= :periodEnd',
+      { periodStart: '2026-06-29', periodEnd: '2026-07-31' },
+    );
+    const savedCalls = (billRepo.save as jest.Mock).mock.calls as Array<[Record<string, unknown>]>;
+    expect(Number(savedCalls[0][0].sharedAmount)).toBeCloseTo(300, 0);
+  });
+
   it('mixed → long-term get individual bills, short-term share expenses', async () => {
     // Room 1: two expenses
     (roomExpRepo.createQueryBuilder as jest.Mock).mockReturnValue(

apps/server/src/bills/bills.service.ts

@@ -50,10 +50,10 @@ export class BillsService {
         .execute();
     }
 
-    // 获取所有有费用的宿舍
+    // 获取账单周期内所有有费用的宿舍
     const roomExpenses = await this.roomExpRepo
       .createQueryBuilder('e')
-      .where('e.periodStart = :periodStart AND e.periodEnd = :periodEnd', {
+      .where('e.periodStart >= :periodStart AND e.periodEnd <= :periodEnd', {
         periodStart,
         periodEnd,
       })