HttpClient Socket Exhaustion Fix

TL;DR

Don't new HttpClient() per request. Use IHttpClientFactory.

The Error

System.Net.Sockets.SocketException: Only one usage of each socket address

Root Cause

HttpClient doesn't close sockets immediately. Creating thousands = port exhaustion.

Fix

// Program.cs
builder.Services.AddHttpClient();
// Inject
public class ApiService(IHttpClientFactory factory)
{
var client = factory.CreateClient();
}