fix(app-iced, presenter): M114 r3 —— 登录成功提示走 i18n key+参数，离线名字提交判据与 host 同源

- 新增 Key::AccountLoginSucceeded（Signed in as {name} / 已登录 {name}）：
  presenter 不再拼「已登录：{name}」这类人类可读句子（复审 r1 P1-1 的收尾）
- valid_offline_name 从 host 搬到 dto（UI 与 host 共用的同一个判据），
  Form::offline_ready 改用它：按钮不再「亮着但必然失败」
- 视图模型测试：成功提示按 i18n 渲染进 on_screen；离线提交判据加「太短也拒绝」断言

crates/presenter/src/host/accounts.rs

@@ -21,7 +21,8 @@ use unlucky_core::download::blocking::block_on;
 
 use crate::dto::CoreEvent;
 use crate::dto::{
-    AccountKind, AccountNotice, AccountNoticeCode, AccountView, DeviceLoginView, LoginFailure,
+    valid_offline_name, AccountKind, AccountNotice, AccountNoticeCode, AccountView,
+    DeviceLoginView, LoginFailure,
 };
 
 use super::env::HostEnv;
@@ -33,7 +34,7 @@ pub mod authlib;
 
 mod failure;
 
-pub use failure::{valid_offline_name, AccountFailure};
+pub use failure::AccountFailure;
 
 use failure::classify;