fix: 清理 unused-vars 回归(32→0) + 修复 go:embed 编译阻塞

1. ESLint unused-vars 从 32 清零（回归修复）
   - 删除 14 个文件中未使用的 import（lucide 图标/shadcn 组件/JsonData 类型）
   - 移除未使用的变量/参数（categoryLabels/updateEntry/onSaved 等）
   - 涉及: AppRelease/PipelineEditor/KubernetesNodes/AlertCenter/SilenceRulesPanel 等

2. 修复 go:embed all:static 编译阻塞
   - 新增 backend/static/.gitkeep 占位文件
   - 全新 clone 后 go build ./... 可直接通过（不再依赖先 npm run build）

3. 安装缺失的 npm 依赖
   - react-markdown/remark-gfm（AgentMarkdown 组件）
   - @codemirror/lang-python/@codemirror/legacy-modes（ScriptCodeEditor 组件）

验证: go build✅ | tsc -b✅ | npm build✅(21s) | ESLint any=41 unused=0 | 17/17 集成测试✅

frontend/src/components/monitor/alert-center/AlertCenter.tsx

@@ -32,7 +32,6 @@ import { NotifyPolicyTab } from './NotifyPolicyTab';
 
 import type { UnifiedAlertRule } from '@/api';
 import type { Contact, ContactGroup } from './alert-center-helpers';
-import type { JsonData } from '@/types/common';
 import { useTranslation } from 'react-i18next';
 
 const AlertCenter: React.FC = () => {

frontend/src/components/monitor/alert-center/SilenceRulesPanel.tsx

@@ -1,6 +1,6 @@
 // 告警静默规则面板 — 嵌入通知策略 Tab // Logan.Li
 import { useState, useEffect, useCallback } from 'react';
-import { VolumeX, Plus, RefreshCw, Clock, Calendar, Repeat, Edit, Trash2 } from 'lucide-react';
+import { VolumeX, Plus, RefreshCw, Edit, Trash2 } from 'lucide-react';
 import { Button } from '@/components/ui/button';
 import { Badge } from '@/components/ui/badge';
 import { Card, CardContent } from '@/components/ui/card';

frontend/src/components/monitor/dashboard/GrafanaDashboard.tsx

@@ -240,7 +240,7 @@ const AgentTab: React.FC = () => {
 
       <AgentWizard open={wizardOpen} onOpenChange={setWizardOpen} server={wizardServer}
         onStart={(id) => { setOperating(prev => new Set(prev).add(id)); }}
-        onInstalled={(id) => { toast.success('Agent 安装任务已提交，后台执行中…'); setWizardOpen(false); fetch(); }}
+        onInstalled={() => { toast.success('Agent 安装任务已提交，后台执行中…'); setWizardOpen(false); fetch(); }}
         onFailed={(id) => { toast.error('安装失败'); setOperating(prev => { const next = new Set(prev); next.delete(id); return next; }); }} />
 
       {/* ────────── 批量部署 Agent 对话框 ────────── */}

frontend/src/components/monitor/datasource/PrometheusDatasourceManager.tsx

@@ -6,7 +6,6 @@ import {
   Edit,
   Trash2,
   Star,
-  RefreshCw,
   Key,
   Plug,
 } from 'lucide-react';