feat: use six-digit numeric member invite codes

docs/注册登录对接文档.md

@@ -31,12 +31,12 @@ Content-Type: application/json
   "username": "alice01",
   "phone": "13800138000",
   "password": "Secret123",
-  "referral_code": "ABCD2345",
+  "referral_code": "123456",
   "privacy_accepted": true
 }
 ```
 
-`referral_code` 可选；传入时必须匹配当前租户下正常会员的 `invite_code`。
+`referral_code` 必填，必须是 6 位数字，且匹配当前租户下正常会员的 `invite_code`。邀请链接可通过 `inviteCode`、`invite_code` 或 `referral_code` 参数预填注册表单。
 
 ## 4 登录
 
@@ -64,7 +64,7 @@ Content-Type: application/json
     "member_no": "MABCDEFGHIJKLMNOPQRST",
     "username": "alice01",
     "phone": "13800138000",
-    "invite_code": "EFGH6789",
+    "invite_code": "654321",
     "token": "...",
     "token_type": "Bearer",
     "expires_at": "2026-10-23T10:00:00Z"
@@ -92,7 +92,7 @@ Authorization: Bearer <token>
 | `USERNAME_INVALID_FORMAT` | 400 | 账户名格式错误 |
 | `PHONE_INVALID_FORMAT` | 400 | 手机号格式错误 |
 | `PASSWORD_INVALID_FORMAT` | 400 | 密码格式错误 |
-| `REFERRAL_CODE_INVALID` | 400 | 推荐码无效 |
+| `REFERRAL_CODE_INVALID` | 400 | 邀请码为空、格式错误或不存在 |
 | `PRIVACY_POLICY_NOT_ACCEPTED` | 400 | 未同意隐私政策 |
 | `ACCOUNT_ALREADY_REGISTERED` | 409 | 账户名或手机号已注册 |
 | `INVALID_CREDENTIALS` | 401 | 手机号或密码错误 |