Fix contact form data

We also use the contact form to report various errors on the website.
To facilitate communication and better understand the problem,
we collect some basic information about user's client (browser).

Migrating to Fly introduced a bit of confusion with the IP address.
In most hostings we can get it using:

```ruby
request.remote_ip
request.remote_addr
```

or

```ruby
request.env['HTTP_X_REAL_IP']
request.env['REMOTE_ADDR']
```

However, research showed me that Fly has a custom field in the header.
For posterity, I have kept the most important links: [1] [2] [3] [4]

So the "Fly-Client-IP" field can be found in Rails under
`request.env['HTTP_FLY_CLIENT_IP']`, which doesn't seem intuitive to me.

[1]: https://fly.io/docs/reference/runtime-environment/#request-headers
[2]: https://community.fly.io/t/how-to-retreive-the-real-ip-address-of-an-http-request-with-v2-app-with-http-service-configuration/12095
[3]: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For
[4]: https://stackoverflow.com/questions/10997005/whats-the-difference-between-request-remote-ip-and-request-ip-in-rails

app/controllers/contact_forms_controller.rb

@@ -6,6 +6,7 @@ def new
   end
 
   def create
+    request.remote_ip = request.env['HTTP_FLY_CLIENT_IP'] || request.remote_ip
     @contact_form = ContactForm.new(params[:contact_form])
     @contact_form.request = request
     @contact_form.deliver ? flash[:notice] = t('.success') : flash[:alert] = t('.fail')