refactor: extract pay page components and migrate zpay → easypay

Components:
- Add PayPageLayout, OrderFilterBar, MobileOrderList, OrderTable, OrderSummaryCards
- Extract shared pay-utils (types, constants, helper functions)
- Simplify pay/page.tsx and orders/page.tsx

EasyPay migration:
- Remove src/lib/zpay/, api/zpay/notify, zpay test, zpay.md
- Simplify config.ts: single envSchema, no ZPAY_* fallback
- Rename DB field zpay_trade_no → payment_trade_no (migration added)
- Update OrderDetail label: ZPAY订单号 → 支付单号
- Update CLAUDE.md project structure

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

@@ -1,56 +0,0 @@
-import { describe, it, expect } from 'vitest';
-import { generateSign, verifySign } from '@/lib/zpay/sign';
-
-describe('ZPAY Sign', () => {
-  const pkey = 'YifxyCWYTLW3hXD4Ae7xB9KqtVA2474k';
-
-  it('should generate correct sign with sorted params', () => {
-    const params = {
-      pid: '2026022720004756',
-      type: 'alipay',
-      out_trade_no: '20160806151343349',
-      notify_url: 'http://www.aaa.com/notify_url.php',
-      name: 'test product',
-      money: '1.00',
-      return_url: 'http://www.aaa.com/return_url.php',
-    };
-    const sign = generateSign(params, pkey);
-    expect(sign).toMatch(/^[a-f0-9]{32}$/); // md5 lowercase hex
-  });
-
-  it('should filter out empty values, sign and sign_type', () => {
-    const params = {
-      a: '1',
-      b: '',
-      sign: 'xxx',
-      sign_type: 'MD5',
-      c: '3',
-    };
-    const sign = generateSign(params, pkey);
-    // Should only use a=1&c=3 + pkey
-    const expected = generateSign({ a: '1', c: '3' }, pkey);
-    expect(sign).toBe(expected);
-  });
-
-  it('should sort params by ASCII order', () => {
-    const params1 = { z: '1', a: '2', m: '3' };
-    const params2 = { a: '2', m: '3', z: '1' };
-    expect(generateSign(params1, pkey)).toBe(generateSign(params2, pkey));
-  });
-
-  it('should verify valid signature', () => {
-    const params = { a: '1', b: '2' };
-    const sign = generateSign(params, pkey);
-    expect(verifySign(params, pkey, sign)).toBe(true);
-  });
-
-  it('should reject invalid signature', () => {
-    const params = { a: '1', b: '2' };
-    expect(verifySign(params, pkey, 'invalidsignature1234567890123456')).toBe(false);
-  });
-
-  it('should reject signature with wrong length', () => {
-    const params = { a: '1', b: '2' };
-    expect(verifySign(params, pkey, 'short')).toBe(false);
-  });
-});