feat: 前端离线部署适配与在线模型测试延迟展示

- 移除 index.html 中 Google Fonts 外链，适配离线部署环境
- 侧边栏用户头像改为显示姓名首字母，去掉 picsum 占位图外链
- 在线模型测试补充 latency_ms 延迟字段展示
- api_key 为空时传空字符串避免校验报错

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

frontend/src/api/modules/model.ts

@@ -107,7 +107,13 @@ export const testOnlineModel = (data: {
   api_key: string
   online_model_name: string
 }) =>
-  post<{ success: boolean; error?: string; model?: string; usage?: object }>(
+  post<{
+    success: boolean
+    error?: string
+    model?: string
+    usage?: object
+    latency_ms?: number
+  }>(
     '/model-manage/test-online',
     data,
   )

frontend/src/components/AppSidebar.vue

@@ -180,7 +180,7 @@ async function handleLogout() {
     <!-- 底部信息 -->
     <div class="sidebar-footer">
       <div class="footer-user" v-if="auth.username">
-        <el-avatar :size="36" src="https://picsum.photos/id/1005/36/36" class="user-avatar" />
+        <el-avatar :size="36" class="user-avatar">{{ auth.displayName?.slice(0, 1) || '?' }}</el-avatar>
         <div class="user-info">
           <span class="user-name">{{ auth.displayName }}</span>
           <span class="user-role">{{ auth.roleLabel }}</span>

frontend/src/views/model/ModelCreateView.vue

@@ -38,7 +38,13 @@ const form = reactive<ModelForm>({
 
 // 在线模型测试
 const testLoading = ref(false)
-const testResult = ref<{ success: boolean; error?: string; model?: string; usage?: object } | null>(null)
+const testResult = ref<{
+  success: boolean
+  error?: string
+  model?: string
+  usage?: object
+  latency_ms?: number
+} | null>(null)
 
 const rules: FormRules = {
   name: [
@@ -149,7 +155,7 @@ async function handleTestOnline() {
     const start = Date.now()
     const res = await testOnlineModel({
       api_url: form.api_url,
-      api_key: form.api_key,
+      api_key: form.api_key || '',
       online_model_name: form.online_model_name,
     })
     const data = res as any