feat: improve application access and money precision

api/src/billing/billing.service.spec.ts

@@ -61,6 +61,16 @@ describe('BillingService', () => {
         amountCents: 20,
       }),
     );
+
+    expect(
+      service.estimateSmsCost({ tenantId: 'tenant-1', content: '四位小数单价', phoneCount: 2, unitPrice: 325 }),
+    ).toEqual(
+      expect.objectContaining({
+        unitPrice: 325,
+        totalBillingUnits: 2,
+        amountCents: 650,
+      }),
+    );
   });
 
   it('allows sending only when cash balance plus credit is greater than zero', async () => {
@@ -81,7 +91,7 @@ describe('BillingService', () => {
     await expect(service.checkAccount({ tenantId: 'tenant-1', amountCents: 999999 })).resolves.toEqual(
       expect.objectContaining({ availableAmount: 1500, creditCents: 500, canSend: true }),
     );
-    await expect(service.updateCreditLimit('tenant-1', { creditCents: 1.5 })).rejects.toThrow('授信额度必须为整数金额');
+    await expect(service.updateCreditLimit('tenant-1', { creditCents: 1.5 })).rejects.toThrow('授信额度最多支持人民币小数点后 4 位');
     expect(prisma.operationLog.create).toHaveBeenCalledWith({
       data: expect.objectContaining({
         action: 'billing.credit_limit_updated',