feat: 重新设计登录框

- 记住上次选的班级（机房一节课一个班），打开就带出这个班的名单；不记姓名
- 姓名可以打字筛选，选好后光标自动跳到密码框
- 三个报错框合成一处；“管理员登录”改成“老师”；密码可以点眼睛看；加“忘了密码找老师重置”

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/components/Login.vue

@@ -2,12 +2,13 @@
   <n-modal
     preset="card"
     title="登录"
-    style="width: 420px"
+    style="width: min(400px, 92vw)"
+    :bordered="false"
     v-model:show="loginModal"
   >
     <n-tabs v-model:value="activeTab" @update:value="onTabChange">
-      <n-tab-pane name="student" tab="学生登录">
-        <n-form>
+      <n-tab-pane name="student" tab="学生">
+        <n-form :show-feedback="false" class="form">
           <n-form-item label="班级">
             <n-select
               v-model:value="selectedClass"
@@ -21,37 +22,25 @@
             <n-select
               v-model:value="selectedUsername"
               :options="nameOptions"
-              placeholder="选择姓名"
+              filterable
+              :placeholder="selectedClass ? '选择或输入姓名' : '先选班级'"
               :loading="namesLoading"
               :disabled="!selectedClass || namesLoading"
+              @update:value="focusPassword"
             />
           </n-form-item>
           <n-form-item label="密码">
             <n-input
+              ref="studentPasswordRef"
               type="password"
+              show-password-on="click"
               v-model:value="studentPassword"
               name="password"
+              placeholder="输入密码，按 Enter 登录"
               @keyup.enter="submitStudent"
             />
           </n-form-item>
-          <n-alert
-            type="error"
-            v-if="classesError"
-            class="message"
-            title="加载班级列表失败，请刷新重试"
-          />
-          <n-alert
-            type="error"
-            v-if="namesError"
-            class="message"
-            title="加载姓名列表失败，请重新选择班级"
-          />
-          <n-alert
-            type="error"
-            v-if="studentError"
-            class="message"
-            :title="studentError"
-          />
+          <div v-if="studentError" class="error">{{ studentError }}</div>
           <n-button
             block
             type="primary"
@@ -61,28 +50,26 @@
           >
             登录
           </n-button>
+          <div class="note">忘了密码找老师重置</div>
         </n-form>
       </n-tab-pane>
 
-      <n-tab-pane name="admin" tab="管理员登录">
-        <n-form>
+      <n-tab-pane name="admin" tab="老师">
+        <n-form :show-feedback="false" class="form">
           <n-form-item label="用户名">
-            <n-input v-model:value="adminName" name="username" />
+            <n-input v-model:value="adminName" name="username" placeholder="用户名" />
           </n-form-item>
           <n-form-item label="密码">
             <n-input
               type="password"
+              show-password-on="click"
               v-model:value="adminPassword"
               name="password"
+              placeholder="输入密码，按 Enter 登录"
               @keyup.enter="submitAdmin"
             />
           </n-form-item>
-          <n-alert
-            type="error"
-            v-if="adminError"
-            class="message"
-            :title="adminError"
-          />
+          <div v-if="adminError" class="error">{{ adminError }}</div>
           <n-button
             block
             type="primary"
@@ -99,14 +86,17 @@
 </template>
 
 <script lang="ts" setup>
-import { ref, computed, onMounted } from "vue"
+import { ref, computed, nextTick, onMounted } from "vue"
 import { Account } from "../api"
 import { loginModal } from "../store/modal"
 import { user } from "../store/user"
 import { router } from "../router"
 
-// Tab state
+// 机房的电脑一节课一个班轮流用：记住班级，不记姓名
+const CLASS_KEY = "login-class"
+
 const activeTab = ref("student")
+const studentPasswordRef = ref<{ focus: () => void } | null>(null)
 
 // Student tab state
 const selectedClass = ref<string | null>(null)
@@ -115,10 +105,8 @@ const studentPassword = ref("")
 const studentLoading = ref(false)
 const studentError = ref("")
 
-// Classes data
 const classes = ref<string[]>([])
 const classesLoading = ref(false)
-const classesError = ref(false)
 const classOptions = computed(() =>
   classes.value.map((c) => ({ label: c, value: c })),
 )
@@ -126,7 +114,6 @@ const classOptions = computed(() =>
 // Names data
 const names = ref<{ name: string; username: string }[]>([])
 const namesLoading = ref(false)
-const namesError = ref(false)
 const nameOptions = computed(() =>
   names.value.map((n) => ({ label: n.name, value: n.username })),
 )
@@ -137,28 +124,31 @@ const adminPassword = ref("")
 const adminLoading = ref(false)
 const adminError = ref("")
 
-// Load classes on mount (cached — not reloaded on tab switch)
+// 班级列表只在打开页面时取一次
 onMounted(async () => {
   classesLoading.value = true
-  classesError.value = false
   try {
     classes.value = await Account.listClasses()
   } catch {
-    classesError.value = true
+    studentError.value = "班级列表没加载出来，请刷新页面重试"
+    return
   } finally {
     classesLoading.value = false
   }
+  let saved: string | null = null
+  try {
+    saved = localStorage.getItem(CLASS_KEY)
+  } catch {}
+  if (saved && classes.value.includes(saved)) {
+    selectedClass.value = saved
+    onClassChange(saved)
+  }
 })
 
+// 换标签页时清掉输入的密码和错误；选好的班级和姓名留着
 function onTabChange() {
-  // Reset student tab state
-  selectedClass.value = null
-  selectedUsername.value = null
   studentPassword.value = ""
   studentError.value = ""
-  namesError.value = false
-  names.value = []
-  // Reset admin tab state
   adminName.value = ""
   adminPassword.value = ""
   adminError.value = ""
@@ -167,17 +157,24 @@ function onTabChange() {
 async function onClassChange(classname: string) {
   selectedUsername.value = null
   names.value = []
-  namesError.value = false
+  studentError.value = ""
+  try {
+    localStorage.setItem(CLASS_KEY, classname)
+  } catch {}
   namesLoading.value = true
   try {
     names.value = await Account.listNamesByClass(classname)
   } catch {
-    namesError.value = true
+    studentError.value = "姓名列表没加载出来，请重新选一次班级"
   } finally {
     namesLoading.value = false
   }
 }
 
+function focusPassword() {
+  nextTick(() => studentPasswordRef.value?.focus())
+}
+
 // 失败次数太多被暂时禁止登录时，显示服务端给的提示
 function loginError(err: any, fallback: string) {
   return err.response?.status === 429 ? err.response.data.detail : fallback
@@ -228,7 +225,24 @@ async function submitAdmin() {
 </script>
 
 <style scoped>
-.message {
-  margin-bottom: 12px;
+.form {
+  display: flex;
+  flex-direction: column;
+  gap: 12px;
+  padding-top: 4px;
+}
+
+.error {
+  padding: 6px 10px;
+  border-radius: 6px;
+  font-size: 13px;
+  color: var(--wp-bad);
+  background: var(--wp-bad-soft);
+}
+
+.note {
+  font-size: 12px;
+  text-align: center;
+  color: var(--wp-faint);
 }
 </style>