♻️ refactor(admin): 统一使用GitMerge图标

- 移除FileMerge图标导入
- 在WordMerge页面将合并按钮图标从FileMerge替换为GitMerge
- 保持功能不变，统一图标风格

src/client/admin/menu.tsx

@@ -14,7 +14,6 @@ import {
   Wallet,
   LayoutTemplate,
   UserPlus,
-  FileMerge,
   GitMerge
 } from 'lucide-react';
 

src/client/admin/pages/WordMerge.tsx

@@ -2,7 +2,7 @@ import React, { useState, useRef } from 'react';
 import { Button } from '@/client/components/ui/button';
 import { Card, CardContent, CardHeader, CardTitle } from '@/client/components/ui/card';
 import { toast } from 'sonner';
-import { Upload, Download, Trash2, FileText } from 'lucide-react';
+import { Upload, Download, Trash2, FileText, GitMerge } from 'lucide-react';
 
 interface WordFile {
   id: string;
@@ -217,7 +217,7 @@ const WordMergePage: React.FC = () => {
                 disabled={files.length < 2 || isMerging}
                 className="w-full"
               >
-                <FileMerge className="h-4 w-4 mr-2" />
+                <GitMerge className="h-4 w-4 mr-2" />
                 {isMerging ? '合并中...' : `合并文档 (${files.length})`}
               </Button>