Add production docker file for backend

src/backend/server/Dockerfile

@@ -0,0 +1,27 @@
+FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base
+WORKDIR /app
+EXPOSE 80
+EXPOSE 443
+
+FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
+WORKDIR /src
+
+COPY *.sln .
+COPY ["src/Todo.Api/Todo.Api.csproj", "src/Todo.Api/"]
+COPY ["src/Todo.Core/Todo.Core.csproj", "src/Todo.Core/"]
+COPY ["src/Todo.Persistence/Todo.Persistence.csproj", "src/Todo.Persistence/"]
+
+RUN dotnet restore .
+
+COPY . .
+
+WORKDIR "src/Todo.Api"
+RUN dotnet build . -c Release -o /app/build
+
+FROM build AS publish
+RUN dotnet publish "Todo.Api.csproj" -c Release -o /app/publish
+
+FROM base AS final
+WORKDIR /app
+COPY --from=publish /app/publish .
+ENTRYPOINT ["dotnet", "Todo.Api.dll"]