feat(dcauth): 移除机器码，改用纯设备码认证

- DCAuth 协议升级到 v2，签名原文只含设备码；客户端 2.0.0，旧版本返回 426
- 删除客户端机器码采集、后端 machine_code_* 字段与日志、后台机器码展示
- 102 迁移在生产执行前直接改为无机器码结构；SQL 守卫仅放行该文件
- Mock 短信不启用每日限额；修复慢电脑首次启动的协议转发竞态
- 新增 macOS DCAuth.app 打包脚本，注册 dcauth:// 协议，浏览器可直接唤起

apps/backend/src/services/admin/admin-auth-service.ts

@@ -256,9 +256,7 @@ export async function completeAdminLogin(
   })
   await ensureAdminDeviceBinding(Number(user.id), consumed)
 
-  return createAdminLoginSession(user, consumed.device_id, meta, {
-    machineCodeMask: consumed.machine_code_mask,
-  })
+  return createAdminLoginSession(user, consumed.device_id, meta)
 }
 
 async function createAdminLoginSession(
@@ -269,7 +267,6 @@ async function createAdminLoginSession(
     userAgent?: string
     location?: string
   },
-  extra: { machineCodeMask?: string } = {},
 ): Promise<JsonObject> {
   const session = createAdminSession(user, deviceId)
   const createdSession = await createAdminSessionRecord({
@@ -292,7 +289,6 @@ async function createAdminLoginSession(
     role: normalizeAdminRole(user.role),
     success: true,
     loginMethod: 'sms_device',
-    machineCodeMask: String(extra.machineCodeMask || ''),
     ...pickLoginMeta(meta),
   })
   return session
@@ -959,7 +955,6 @@ function mapAdminUser(user: AdminUserRow): JsonObject {
     deviceBound: Boolean(user.device_id),
     deviceId: String(user.device_id || ''),
     deviceIdMasked: maskDeviceId(user.device_id),
-    machineCodeMask: String(user.machine_code_mask || ''),
     deviceBoundAt: user.device_bound_at || null,
     deviceLastUsedAt: user.device_last_used_at || null,
     createdAt: user.created_at,