Cinny includes nginx configuration which does URL rewrites now, as seen
here: https://raw.githubusercontent.com/cinnyapp/cinny/dev/docker-nginx.conf

That said, we have our own nginx configuration for Cinny, because we'd
like to run ngin as non-root and on a non-privileged port (80 -> 8080).

For this reason, we override `/etc/nginx/nginx.conf` and need to
duplicate what we see in `/etc/nginx/conf.d/default.conf` with our own
`server` block (which listens on port 8080).

Most of these files were defining a service, usually toward the end.
These lines have been moved upward.

Some components (mautrix-signal, mautrix-gmessages, etc.) were defining
a service conditionally (only if metrics are exposed, etc). This was
causing issues like these in the Traefik logs:

> level=error msg="service \"matrix-mautrix-twitter\" error: port is missing" providerName=docker container=matrix-mautrix-twitter-..

Previously, it had to go through matrix-nginx-proxy.
It's exposed to Traefik directly via container labels now

This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.