feat(infra): add LmxFakeProxy Dockerfile and docker-compose service

infra/lmxfakeproxy/Dockerfile

@@ -0,0 +1,12 @@
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+COPY LmxFakeProxy.csproj .
+RUN dotnet restore
+COPY . .
+RUN dotnet publish -c Release -o /app
+
+FROM mcr.microsoft.com/dotnet/aspnet:10.0
+WORKDIR /app
+COPY --from=build /app .
+EXPOSE 50051
+ENTRYPOINT ["dotnet", "LmxFakeProxy.dll"]