Invalid CSRF token with Docker Compose setup

I'm having a slightly similar problem to this issue: https://github.com/wallabag/docker/issues/397

I just setup Wallabag with docker compose as follows:

```
services:
wallabag:
image: wallabag/wallabag
container_name: wallabag-server
env_file: ./wallabag.env
volumes:
- ./data/app/images:/var/www/wallabag/web/assets/images
networks:
- traefik
- wallabag
restart: unless-stopped
labels:
- "diun.enable=true"

- "traefik.enable=true"
- "traefik.docker.network=traefik"
- "traefik.http.routers.wallabag.rule=Host(`wallabag.example.com`)"
- "traefik.http.routers.wallabag.entrypoints=https"
- "traefik.http.routers.wallabag.tls.certResolver=letls"
healthcheck:
test: ["CMD", "wget" ,"--no-verbose", "--tries=1", "--spider", "http://localhost/api/info"]
interval: 1m
timeout: 3s
depends_on:
- db
- redis
db:
image: mariadb
container_name: wallabag-db
restart: unless-stopped
env_file: ./wallabag.env
volumes:
- ./data/db:/var/lib/mysql
healthcheck:
test: ["CMD", "mysqladmin" ,"ping", "-h", "localhost"]
interval: 20s
timeout: 3s
networks:
- wallabag
labels:
- "diun.enable=true"
redis:
image: redis:alpine
container_name: wallabag-redis
restart: unless-stopped
healthcheck:
test: ["CMD", "redis-cli", "ping"]
interval: 20s
timeout: 3s
networks:
- wallabag
labels:
- "diun.enable=true"
networks:
traefik:
external: true
name: traefik
wallabag:
external: true
name: wallabag
```

I can log in with the default wallabag username and password (with no **Invalid CSRF Token**), I created another account, signed out and attempted to sign in, but get: **Invalid CSRF Token**. It goes back to the log in page. However, if a go to https://wallabag.example.com/quickstart - my new user is signed in.

My setup is behind Cloudflare.

Start by reproducing the login flow with the supplied Docker Compose configuration, noting that the default account succeeds while the newly created account fails and /quickstart remains authenticated. Compare the behavior with wallabag/docker#397 and check the Cloudflare and Traefik-proxied setup; done means the new account can sign in without an Invalid CSRF Token.

Written by the indexing model from the issue text.