fix(order-service): 修复包含 Emoji 和孤立代理字符的订单在 PostgreSQL jsonb 下报错导致死循环重试进单的问题

1. 在 utils/json.ts 新增 sanitizeWellFormedUnicode、deepSanitizeUnicode 和 safeJsonStringify，自动清理空字节 (\0) 并将畸变孤立 UTF-16 代理字符 (Lone Surrogates) 安全转换为规范字符，杜绝 PostgreSQL jsonb 解析错误；
2. 拼多多订单映射器与通用进单服务 (order-service) 全面接入 Unicode 深度清洗与安全序列化，确保买家昵称/留言中的各类特殊 Emoji 和生僻字符平滑落库；
3. 数据库仓储层 (order-repo / order-item-repo) 针对 raw_payload_json、spec_json、item_snapshot_json 等 jsonb 字段增加兜底安全序列化保护；
4. 补充 utils/json.test.ts 与 pdd-order-mapper.test.ts 单元测试，覆盖畸变字符与空字节场景。

apps/backend/src/utils/json.test.ts

@@ -0,0 +1,55 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import {
+  parseJsonObject,
+  sanitizeWellFormedUnicode,
+  deepSanitizeUnicode,
+  safeJsonStringify,
+} from './json.js'
+
+test('sanitizeWellFormedUnicode handles null bytes and lone surrogates', () => {
+  // Null byte
+  assert.equal(sanitizeWellFormedUnicode('hello\0world'), 'helloworld')
+
+  // Lone high surrogate \ud835
+  const loneSurrogate = 'nickname\ud835test'
+  const cleaned = sanitizeWellFormedUnicode(loneSurrogate)
+  assert.equal(cleaned, 'nickname\uFFFDtest')
+
+  // Valid emoji surrogate pair \uD83D\uDE00 (😀) should remain intact
+  const validEmoji = 'Hello 😀'
+  assert.equal(sanitizeWellFormedUnicode(validEmoji), 'Hello 😀')
+})
+
+test('deepSanitizeUnicode recursively cleans objects and arrays', () => {
+  const input = {
+    user: 'buyer\ud83c',
+    nested: {
+      comment: 'good\0deal',
+      tags: ['cool\ud835', 'ok'],
+    },
+  }
+
+  const output = deepSanitizeUnicode(input)
+  assert.deepEqual(output, {
+    user: 'buyer\uFFFD',
+    nested: {
+      comment: 'gooddeal',
+      tags: ['cool\uFFFD', 'ok'],
+    },
+  })
+})
+
+test('safeJsonStringify produces valid JSON safe for postgres jsonb', () => {
+  const input = {
+    orderSn: '260919-123456',
+    nickname: '\ud835\ud83c*buyer',
+    nullByte: 'abc\0def',
+  }
+
+  const json = safeJsonStringify(input)
+  assert.ok(typeof json === 'string')
+  const parsed = JSON.parse(json)
+  assert.equal(parsed.nickname, '\uFFFD\uFFFD*buyer')
+  assert.equal(parsed.nullByte, 'abcdef')
+})