feat: support nickname login and nickname uniqueness check v0.0.3

- Login: query user by name field, authenticate with username
- Register: add blur-triggered nickname uniqueness validation
- Requires PocketBase users collection listRule/viewRule set to public

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/views/Login.vue

@@ -4,6 +4,7 @@ import { ref } from 'vue'
 import { useRouter } from 'vue-router'
 import { useUserStore } from '@/stores/user'
 import { ElMessage } from 'element-plus'
+import { pb } from '@/api/pocketbase'
 import PasswordInput from '@/components/common/PasswordInput.vue'
 
 const router = useRouter()
@@ -15,16 +16,29 @@ const loading = ref(false)
 
 async function handleLogin() {
   if (!identity.value || !password.value) {
-    ElMessage.warning('请输入邮箱和密码')
+    ElMessage.warning('请输入昵称/邮箱和密码')
     return
   }
 
   try {
     loading.value = true
-    await userStore.login(identity.value, password.value)
+    let loginIdentity = identity.value.trim()
 
-    const redirect = '/'
-    router.push(redirect)
+    // 如果不包含 @，按昵称或用户名查找对应 username 用于认证
+    if (!loginIdentity.includes('@')) {
+      const result = await pb.collection('users').getList(1, 1, {
+        filter: `name="${loginIdentity}" || username="${loginIdentity}"`,
+        $autoCancel: false
+      })
+      if (result.items.length === 0) {
+        ElMessage.error('用户不存在')
+        return
+      }
+      loginIdentity = (result.items[0] as any).username
+    }
+
+    await userStore.login(loginIdentity, password.value)
+    router.push('/')
   } catch (error: any) {
     ElMessage.error(error.message || '登录失败')
   } finally {
@@ -45,12 +59,11 @@ async function handleLogin() {
 
       <form class="login-form" @submit.prevent="handleLogin">
         <div class="form-group">
-          <label for="identity">邮箱</label>
+          <label for="identity">昵称 / 邮箱</label>
           <el-input
             id="identity"
             v-model="identity"
-            type="email"
-            placeholder="请输入注册时的邮箱"
+            placeholder="请输入昵称或邮箱"
             required
           />
         </div>

frontend/src/views/Register.vue

@@ -3,6 +3,7 @@
 import { ref, computed } from 'vue'
 import { useRouter } from 'vue-router'
 import { useUserStore } from '@/stores/user'
+import { pb } from '@/api/pocketbase'
 import PasswordInput from '@/components/common/PasswordInput.vue'
 
 const router = useRouter()
@@ -17,6 +18,21 @@ const formError = ref('')
 
 // ── 实时校验 ──
 const nicknameOk = computed(() => nickname.value.length >= 2 && nickname.value.length <= 16)
+const nicknameTaken = ref(false)
+const nicknameChecking = ref(false)
+
+async function checkNickname() {
+  const val = nickname.value.trim()
+  if (!val || val.length < 2) { nicknameTaken.value = false; return }
+  try {
+    nicknameChecking.value = true
+    const result = await pb.collection('users').getList(1, 1, {
+      filter: `name="${val}"`,
+      $autoCancel: false
+    })
+    nicknameTaken.value = result.items.length > 0
+  } catch { /* ignore */ } finally { nicknameChecking.value = false }
+}
 
 const hasLetter = computed(() => /[a-zA-Z]/.test(password.value))
 const hasDigit = computed(() => /[0-9]/.test(password.value))
@@ -46,6 +62,10 @@ async function handleRegister() {
     formError.value = '昵称需 2-16 个字符'
     return
   }
+  if (nicknameTaken.value) {
+    formError.value = '该昵称已被使用'
+    return
+  }
   if (!passwordOk.value) {
     formError.value = '密码不符合要求'
     return
@@ -89,7 +109,10 @@ async function handleRegister() {
         <!-- 昵称 -->
         <div class="form-group">
           <label for="nickname">昵称</label>
-          <el-input id="nickname" v-model="nickname" placeholder="2-16 个字符，支持中文" required />
+          <el-input id="nickname" v-model="nickname" placeholder="2-16 个字符，支持中文" required @blur="checkNickname" />
+          <span v-if="nicknameChecking" class="field-hint">检查中...</span>
+          <span v-else-if="nicknameTaken && nickname.length >= 2" class="field-hint error">该昵称已被使用</span>
+          <span v-else-if="nicknameOk && nickname" class="field-hint ok">昵称可用</span>
           <div class="field-rules">
             <span class="rule" :class="{ ok: nicknameOk && nickname }">2-16 个字符，支持中英文</span>
           </div>
@@ -259,6 +282,10 @@ async function handleRegister() {
   color: var(--gg-danger);
 }
 
+.field-hint.ok {
+  color: var(--gg-primary);
+}
+
 /* ── 密码强度 ── */
 .password-strength {
   display: flex;