feat(tenant-platform): add docs site link to header

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tenant-platform/src/views/layout/MainLayout.vue

@@ -29,6 +29,12 @@
     <el-container>
       <el-header class="header">
         <div class="header-right">
+          <el-tooltip content="开发者文档" placement="bottom">
+            <a href="/docs/" target="_blank" class="docs-link">
+              <el-icon :size="18"><Document /></el-icon>
+              <span>文档</span>
+            </a>
+          </el-tooltip>
           <el-dropdown @command="handleCommand">
             <span class="user-info">
               <el-avatar :size="32" style="background:#409eff">
@@ -55,6 +61,7 @@
 <script setup lang="ts">
 import { useAuthStore } from '@/stores/auth'
 import { useRouter } from 'vue-router'
+import { Document } from '@element-plus/icons-vue'
 
 const auth = useAuthStore()
 const router = useRouter()
@@ -94,7 +101,22 @@ function handleCommand(cmd: string) {
 .header-right {
   display: flex;
   align-items: center;
-  gap: 12px;
+  gap: 16px;
+}
+.docs-link {
+  display: flex;
+  align-items: center;
+  gap: 4px;
+  color: #555;
+  font-size: 13px;
+  text-decoration: none;
+  padding: 4px 8px;
+  border-radius: 6px;
+  transition: background 0.15s;
+}
+.docs-link:hover {
+  background: #f5f5f5;
+  color: #409eff;
 }
 .user-info {
   display: flex;