feat: add login authentication and certificate expiry notifications

- JWT-based login with ADMIN_USER/ADMIN_PASSWORD env config
- Login page with auth guard for Vue frontend
- Feishu bot webhook notification for expiring certificates
- SMTP email notification for expiring certificates
- Daily 8:00 AM cron for expiry checks
- Startup health check notification

frontend/src/views/Login.vue

@@ -0,0 +1,145 @@
+<template>
+  <div class="login-container">
+    <div class="login-card">
+      <div class="login-header">
+        <el-icon :size="32" color="#1890ff"><Link /></el-icon>
+        <h2>AutoSSL 证书管理</h2>
+        <p class="login-desc">请登录以继续</p>
+      </div>
+      <el-form
+        ref="formRef"
+        :model="form"
+        :rules="rules"
+        label-width="0"
+        @keyup.enter="handleLogin"
+      >
+        <el-form-item prop="username">
+          <el-input
+            v-model="form.username"
+            placeholder="用户名"
+            size="large"
+            :prefix-icon="User"
+          />
+        </el-form-item>
+        <el-form-item prop="password">
+          <el-input
+            v-model="form.password"
+            type="password"
+            placeholder="密码"
+            size="large"
+            show-password
+            :prefix-icon="Lock"
+          />
+        </el-form-item>
+        <el-form-item>
+          <el-button
+            type="primary"
+            size="large"
+            style="width: 100%"
+            :loading="loading"
+            @click="handleLogin"
+          >
+            登 录
+          </el-button>
+        </el-form-item>
+      </el-form>
+      <div class="login-footer">
+        <p v-if="errorMsg" class="error-msg">{{ errorMsg }}</p>
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { ref, reactive } from 'vue'
+import { useRouter } from 'vue-router'
+import { User, Lock } from '@element-plus/icons-vue'
+import { ElMessage } from 'element-plus'
+import { authApi } from '../api'
+
+const router = useRouter()
+const formRef = ref()
+const loading = ref(false)
+const errorMsg = ref('')
+
+const form = reactive({
+  username: '',
+  password: '',
+})
+
+const rules = {
+  username: [{ required: true, message: '请输入用户名', trigger: 'blur' }],
+  password: [{ required: true, message: '请输入密码', trigger: 'blur' }],
+}
+
+const handleLogin = async () => {
+  const valid = await formRef.value.validate().catch(() => false)
+  if (!valid) return
+
+  loading.value = true
+  errorMsg.value = ''
+  try {
+    const res = await authApi.login(form.username, form.password)
+    const { token, username, expires_at } = res.data
+    localStorage.setItem('token', token)
+    localStorage.setItem('username', username)
+    localStorage.setItem('token_expires_at', String(expires_at))
+    ElMessage.success(`欢迎回来, ${username}!`)
+    router.push('/')
+  } catch (e: any) {
+    errorMsg.value = e.response?.data?.error || '登录失败，请检查用户名和密码'
+  } finally {
+    loading.value = false
+  }
+}
+</script>
+
+<style scoped>
+.login-container {
+  min-height: 100vh;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+  background-size: cover;
+}
+
+.login-card {
+  width: 400px;
+  background: white;
+  border-radius: 12px;
+  padding: 40px;
+  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
+}
+
+.login-header {
+  text-align: center;
+  margin-bottom: 32px;
+}
+
+.login-header h2 {
+  margin-top: 12px;
+  font-size: 24px;
+  color: #1a1a2e;
+}
+
+.login-desc {
+  margin-top: 8px;
+  color: #999;
+  font-size: 14px;
+}
+
+.login-footer {
+  text-align: center;
+  margin-top: 8px;
+}
+
+.error-msg {
+  color: #f56c6c;
+  font-size: 13px;
+}
+
+:deep(.el-input__prefix) {
+  font-size: 18px;
+}
+</style>