Get "Please enable cookies." when access from remote host.

# Bug report

Hi,

I'm working on deploying devdocs on no-internet-access internal for our team. We get "Please enable cookies." when someone access devdocs service from their own PC. But, the devdocs service works well when I access it from its hosted server.


I have to say this amazing project is very useful for me and thanks for your guys' contribution.

## Steps to reproduce

Just execute the command as README.
`git clone https://github.com/freeCodeCamp/devdocs.git && cd devdocs`
`docker build -t thibaut/devdocs .`
`docker run --name devdocs -d -p 9292:9292 thibaut/devdocs`

Then, access the service from localhost and a remote host.

You will get `"Please enable cookies."` when you access from remote host and can not save preferences.

You will not get `"Please enable cookies."` when you access via `localhost:9292`

Start with the README Docker instructions and reproduce the difference between localhost:9292 and access from a remote host. Trace the cookie or preference handling involved in that deployment, then verify that remote users no longer see "Please enable cookies." and can save preferences.

索引モデルが issue の本文から書いたものです。