Corrected the .dockerfile to use the correct build image

AdventOfCode/Dockerfile

@@ -1,27 +1,18 @@
-FROM mcr.microsoft.com/dotnet/aspnet:5.0 AS base
+FROM mcr.microsoft.com/dotnet/sdk:5.0 AS build-env
 WORKDIR /app
 EXPOSE 80
 EXPOSE 443
 
-FROM mcr.microsoft.com/dotnet/sdk:5.0 AS build
-WORKDIR /src
-COPY . ./
-RUN dotnet restore
-
-#COPY ["/src/AdventOfCode/AdventOfCode.csproj", "AdventOfCode/"]
-RUN dotnet restore "AdventOfCode.csproj"
-#COPY ["AdventOfCode/", "AdventOfCode/."]
-
+# Copy csproj and restore as distinct layers
 
-RUN dotnet build "AdventOfCode.csproj" -c Release -o /app/build
+COPY . ./
+RUN dotnet publish -c Release -o out
 
-FROM build AS publish
-RUN dotnet publish "./AdventOfCode.csproj" -c Release -o /app/publish
 
-FROM base AS final
+FROM mcr.microsoft.com/dotnet/aspnet:5.0
 WORKDIR /app
-
+COPY --from=build-env /app/out .
 ENV ASPNETCORE_ENVIRONMENT=Production
 ENV ASPNETCORE_URLS=http://+:80
-COPY --from=publish /app/publish .
 ENTRYPOINT ["dotnet", "AdventOfCode.dll"]
+