Configurable bind addresses + display host in Server Settings

ServerConfig grows two fields:
- BindAddresses: list of IPs Kestrel binds to (empty = all interfaces,
  current behavior). Listening only on a subset is useful when the host
  has multiple NICs and the webhook should not be reachable on all of
  them.
- DisplayHost: the hostname/IP the GUI splices into the URL column and
  Copy URL button. Cosmetic; doesn't affect what the server accepts.

Server Settings dialog gains a "Network" section: a checkbox for "all
interfaces" plus per-NIC checkboxes auto-detected via NetworkInterface.
GetAllNetworkInterfaces, and an editable ComboBox for the display host
pre-populated with detected IPs and the machine name.

Listener restart fires on BindAddresses change but not on DisplayHost
change (cosmetic).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/WebhookServer.Service/Program.cs

@@ -36,7 +36,7 @@ try
 
     builder.WebHost.ConfigureKestrel(opts =>
     {
-        opts.ListenAnyIP(initialConfig.HttpPort);
+        ConfigureHttp(opts, initialConfig);
         ConfigureHttps(opts, initialConfig.HttpsBinding);
     });
 
@@ -87,6 +87,24 @@ finally
     Log.CloseAndFlush();
 }
 
+static void ConfigureHttp(Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerOptions opts, ServerConfig cfg)
+{
+    if (cfg.BindAddresses is { Count: > 0 } binds)
+    {
+        foreach (var entry in binds)
+        {
+            if (System.Net.IPAddress.TryParse(entry, out var ip))
+                opts.Listen(ip, cfg.HttpPort);
+            else
+                Log.Warning("Skipping invalid bind address {Entry}", entry);
+        }
+    }
+    else
+    {
+        opts.ListenAnyIP(cfg.HttpPort);
+    }
+}
+
 static void ConfigureHttps(Microsoft.AspNetCore.Server.Kestrel.Core.KestrelServerOptions opts, HttpsBinding? binding)
 {
     if (binding is null || binding.Kind == HttpsBindingKind.None) return;