Fix setup-github-secrets.ps1 syntax error

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/setup-github-secrets.ps1

@@ -10,6 +10,7 @@ $sshKeyPubPath = "$sshKeyPath.pub"
 
 Write-Host "检查 SSH 密钥..." -ForegroundColor Yellow
 
+$useExisting = $false
 if (Test-Path $sshKeyPath) {
     Write-Host "✓ 找到现有 SSH 密钥: $sshKeyPath" -ForegroundColor Green
     $regenerate = Read-Host "是否重新生成? (y/n)"