Update Dockerfile

Author: mxritzdev

LinkRouter/Dockerfile

@@ -3,7 +3,7 @@ WORKDIR /app
 EXPOSE 80
 EXPOSE 443
 
-FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:8.0 AS build
+FROM --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/sdk:9.0 AS build
 ARG BUILD_CONFIGURATION=Release
 WORKDIR /src
 COPY ["LinkRouter/LinkRouter.csproj", "LinkRouter/"]