fix: 加固日历日期与动态错误合同（09-05-error-explainability-payment-readiness，09-08-reimbursement-payment-closeout）

server/tests/unit/routes/paymentBatches.reimbursement.test.js

@@ -1011,6 +1011,42 @@ describe("payment batch reimbursement routes", () => {
     await app.close();
   });
 
+  it("rejects overflowing payment dates before creation writes", async () => {
+    const { app, tx } = await buildApp();
+    try {
+      const response = await app.inject({ method: "POST", url: "/api/payment-batches", headers: { authorization: "Bearer test" },
+        payload: { entityType: "reimbursement", entityIds: [REIMBURSEMENT_ID], defaultPaymentDate: "2026-02-30" } });
+      expect(response.statusCode).toBe(400);
+      expect(response.json().error.details.reasonCode).toBe("payment_batch.invalid_input");
+      expect(response.json().error.details.fieldErrors.defaultPaymentDate).toContain("invalid_calendar_date");
+      expect(tx.paymentBatch.create).not.toHaveBeenCalled();
+      expect(tx.paymentBatchItem.create).not.toHaveBeenCalled();
+      expect(tx.auditLog.create).not.toHaveBeenCalled();
+    } finally { await app.close(); }
+  });
+
+  it.each(["2026-02-30", "2026-13-01"])("rejects invalid payment date override %s without writes", async (paymentDateOverride) => {
+    const { app, tx } = await buildApp();
+    try {
+      const response = await app.inject({ method: "PATCH", url: `/api/payment-batches/${BATCH_ID}/items/${ITEM_ID}`,
+        headers: { authorization: "Bearer test" }, payload: { paymentDateOverride } });
+      expect(response.statusCode).toBe(400);
+      expect(response.json().error.details.fieldErrors.paymentDateOverride).toContain("invalid_calendar_date");
+      expect(tx.paymentBatchItem.update).not.toHaveBeenCalled();
+      expect(tx.auditLog.create).not.toHaveBeenCalled();
+    } finally { await app.close(); }
+  });
+
+  it.each(["2024-02-29", null])("preserves valid or cleared payment date override %s", async (paymentDateOverride) => {
+    const { app, state } = await buildApp();
+    try {
+      const response = await app.inject({ method: "PATCH", url: `/api/payment-batches/${BATCH_ID}/items/${ITEM_ID}`,
+        headers: { authorization: "Bearer test" }, payload: { paymentDateOverride } });
+      expect(response.statusCode).toBe(200);
+      expect(state.batch.items[0].payment_date_override).toEqual(paymentDateOverride ? new Date(`${paymentDateOverride}T00:00:00.000Z`) : null);
+    } finally { await app.close(); }
+  });
+
   it("projects synthetic 0014 omissions in candidates and preflight without writes, and recomputes after repair", async () => {
     const { app, tx, state } = await buildApp();
     const completeOwner = { ...state.reimbursement.owner };