imsapidll48/FIXES_NET48_DUAL_TARGET.md

FIX2 - .NET Framework 4.8 dual target

Changes in this package:

1. IMSApiDotNet.csproj now uses:
   • netstandard2.0
   • net48
2. Added private build-only reference:
   • Microsoft.NETFramework.ReferenceAssemblies.net48 1.0.3
3. Added dedicated build helpers:
   • scripts/build-net48.ps1
   • scripts/build-net48.cmd
4. Added NET48_BUILD.md.
5. Kept the protocol-vector test project on net7.0 so it works with the user's installed .NET SDK 7.0.302.
6. Kept the previous FIX1 compiler corrections in IhapReader.cs and WireRegistry.cs.

Expected Release outputs:

• src/IMSApiDotNet/bin/Release/netstandard2.0/IMSApiDotNet.dll
• src/IMSApiDotNet/bin/Release/net48/IMSApiDotNet.dll

Use the net48 DLL in classic .NET Framework 4.8 applications.