fix: friendly Chinese error messages on login/register pages

Map backend English error details to user-facing Chinese text on all
3 frontends (uni-app, user-frontend, admin-frontend). Previously raw
English like 'Invalid credentials' was shown directly to users.

user-frontend/src/views/WorkspaceLanding.vue

@@ -172,7 +172,8 @@ async function submit() {
     const redirect = route.query.redirect || '/workspace'
     router.push(redirect)
   } catch (e) {
-    error.value = e?.detail || '登录失败'
+    const map = { 'Invalid credentials': '手机号或密码错误', 'Invalid refresh token': '登录已过期，请重新登录', 'phone required': '请输入手机号' }
+    error.value = map[e?.detail] || e?.detail || '登录失败'
   } finally {
     loading.value = false
   }
@@ -191,7 +192,8 @@ async function register() {
     regForm.phone = ''
     regForm.password = ''
   } catch (e) {
-    regError.value = e?.detail || '注册失败'
+    const map = { 'Phone already registered': '该手机号已被注册', 'Invalid credentials': '手机号或密码错误' }
+    regError.value = map[e?.detail] || e?.detail || '注册失败'
   } finally {
     regLoading.value = false
   }