Upgrade Atlasd to net10.0, remove obsolete UseOnlyOverlappedIO

Socket.UseOnlyOverlappedIO was removed in .NET 5+. Overlapped I/O
is the default behavior for async socket operations on modern .NET.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: wjlafrance

src/Atlasd/Atlasd.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>net10.0</TargetFramework>
     <Description>Atlas is cross-platform software that emulates Classic Battle.net in a compatible model for Diablo, StarCraft, and WarCraft.</Description>
     <Copyright>© 2020-2021 Carl Bennett &lt;carl@carlbennett.me&gt;</Copyright>
     <Company>BNETDocs</Company>

src/Atlasd/Battlenet/Protocols/HTTP/HttpListener.cs

@@ -64,7 +64,6 @@ public void Start() /* part of IListener */
             {
                 ExclusiveAddressUse = true,
                 NoDelay = Daemon.Common.TcpNoDelay,
-                UseOnlyOverlappedIO = true,
             };
             Socket.Bind(LocalEndPoint);
             Socket.Listen(-1);

src/Atlasd/Battlenet/ServerSocket.cs

@@ -82,7 +82,6 @@ public void SetLocalEndPoint(IPEndPoint localEndPoint)
             {
                 ExclusiveAddressUse = true,
                 NoDelay = Daemon.Common.TcpNoDelay,
-                UseOnlyOverlappedIO = true,
             };
         }