Make plausible/analytics container port local only

This change makes the container plausible/analytics accessible only from localhost (127.0.0.1). 

I think that this should be the default because:
- to use plausible with a https website, plausible should be served from https. Requires reverse proxy.
- using plausible with http makes it vulnerable to "hackers" when entering admin password and the entire traffic can be seen by "anyone", thus making it insecure.

docker-compose.yml

@@ -30,7 +30,7 @@ services:
       - plausible_events_db
       - mail
     ports:
-      - 8000:8000
+      - 127.0.0.1:8000:8000
     env_file:
       - plausible-conf.env