feat: 集成支付宝电脑网站支付（alipay direct）

- 新增 src/lib/alipay/ 模块：RSA2 签名、网关客户端、AlipayProvider
- 新增 /api/alipay/notify 异步通知回调路由
- config.ts 添加 ALIPAY_* 环境变量
- payment/index.ts 注册 alipaydirect 提供商
- 27 个单元测试全部通过

src/__tests__/lib/alipay/sign.test.ts

@@ -0,0 +1,112 @@
+import { describe, it, expect } from 'vitest';
+import crypto from 'crypto';
+import { generateSign, verifySign } from '@/lib/alipay/sign';
+
+// 生成测试用 RSA 密钥对
+const { publicKey, privateKey } = crypto.generateKeyPairSync('rsa', {
+  modulusLength: 2048,
+  publicKeyEncoding: { type: 'spki', format: 'pem' },
+  privateKeyEncoding: { type: 'pkcs8', format: 'pem' },
+});
+
+// 提取裸 base64（去掉 PEM 头尾）
+const barePrivateKey = privateKey
+  .replace(/-----BEGIN PRIVATE KEY-----/, '')
+  .replace(/-----END PRIVATE KEY-----/, '')
+  .replace(/\n/g, '');
+const barePublicKey = publicKey
+  .replace(/-----BEGIN PUBLIC KEY-----/, '')
+  .replace(/-----END PUBLIC KEY-----/, '')
+  .replace(/\n/g, '');
+
+describe('Alipay RSA2 Sign', () => {
+  const testParams: Record<string, string> = {
+    app_id: '2021000000000000',
+    method: 'alipay.trade.page.pay',
+    charset: 'utf-8',
+    timestamp: '2026-03-05 12:00:00',
+    version: '1.0',
+    biz_content: '{"out_trade_no":"order-001","total_amount":"100.00"}',
+  };
+
+  describe('generateSign', () => {
+    it('should generate a valid RSA2 signature', () => {
+      const sign = generateSign(testParams, privateKey);
+      expect(sign).toBeTruthy();
+      expect(typeof sign).toBe('string');
+      // base64 格式
+      expect(() => Buffer.from(sign, 'base64')).not.toThrow();
+    });
+
+    it('should produce consistent signatures for same input', () => {
+      const sign1 = generateSign(testParams, privateKey);
+      const sign2 = generateSign(testParams, privateKey);
+      expect(sign1).toBe(sign2);
+    });
+
+    it('should filter out sign and sign_type fields', () => {
+      const paramsWithSign = { ...testParams, sign: 'old_sign', sign_type: 'RSA2' };
+      const sign1 = generateSign(testParams, privateKey);
+      const sign2 = generateSign(paramsWithSign, privateKey);
+      expect(sign1).toBe(sign2);
+    });
+
+    it('should filter out empty values', () => {
+      const paramsWithEmpty = { ...testParams, empty_field: '' };
+      const sign1 = generateSign(testParams, privateKey);
+      const sign2 = generateSign(paramsWithEmpty, privateKey);
+      expect(sign1).toBe(sign2);
+    });
+
+    it('should sort parameters alphabetically', () => {
+      const reversed: Record<string, string> = {};
+      const keys = Object.keys(testParams).reverse();
+      for (const key of keys) {
+        reversed[key] = testParams[key];
+      }
+      const sign1 = generateSign(testParams, privateKey);
+      const sign2 = generateSign(reversed, privateKey);
+      expect(sign1).toBe(sign2);
+    });
+  });
+
+  describe('verifySign', () => {
+    it('should verify a valid signature', () => {
+      const sign = generateSign(testParams, privateKey);
+      const valid = verifySign(testParams, publicKey, sign);
+      expect(valid).toBe(true);
+    });
+
+    it('should reject an invalid signature', () => {
+      const valid = verifySign(testParams, publicKey, 'invalid_base64_signature');
+      expect(valid).toBe(false);
+    });
+
+    it('should reject tampered params', () => {
+      const sign = generateSign(testParams, privateKey);
+      const tampered = { ...testParams, total_amount: '999.99' };
+      const valid = verifySign(tampered, publicKey, sign);
+      expect(valid).toBe(false);
+    });
+  });
+
+  describe('PEM auto-formatting', () => {
+    it('should work with bare base64 private key (no PEM headers)', () => {
+      const sign = generateSign(testParams, barePrivateKey);
+      const valid = verifySign(testParams, publicKey, sign);
+      expect(valid).toBe(true);
+    });
+
+    it('should work with bare base64 public key (no PEM headers)', () => {
+      const sign = generateSign(testParams, privateKey);
+      const valid = verifySign(testParams, barePublicKey, sign);
+      expect(valid).toBe(true);
+    });
+
+    it('should work with both bare keys', () => {
+      const sign = generateSign(testParams, barePrivateKey);
+      const valid = verifySign(testParams, barePublicKey, sign);
+      expect(valid).toBe(true);
+    });
+  });
+});