matrix-bot-buscarron: fix username in docs

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1782

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1782

add matrix-bot-buscarron

Make synapse htpasswd file path configurable

.. regardless of whether matrix-nginx-proxy runs in a container or not

Don't self-build signald image on arm64, as upstream image exists

Update path to signald Dockerfile

When setting `matrix_nginx_proxy_enabled: false` and enabling authentication on the metrics endpoint, the htpasswd file is hardcoded to the nginx-proxy container dir, this changes the hardcoded value to a variable so the path can be updated

Bump signald to 0.18.1

According to https://signald.org/articles/install/docker/#migrating-from-versions-before-0180,
This release only chowns files if the container is running as root. See also this upstream commit:
3bb7e8d2c1

Upgrade Heisenbridge (1.10.1 -> 1.12.0)

Change list of public servers, old as not functional

The old link returned a 404 so I thought I throw in joinmatrix.org :)

The maunium fork of Signald is no longer up-to-date (does not publish
0.18.0.. at least not yet) and all the necessary changes are now upstream.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1775

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1775

Related to https://signald.org/articles/install/docker/#migrating-from-versions-before-0180

> Prior to 0.18.0 the signald container image used the root user, which is not recommended for security reasons. This was fixed in the 0.18.0 release which will start as root, fix permissions on the volume, then drop to the non-root user and start signald. Future images will start as the non-root user, so if you’re upgrading make sure to run 0.18.0 at least once.
> A special tag, 0.18.0-non-root, will be published. it starts as the non-root user and does not fix permissions on the volume.

This reverts commit 986fe779cd.

The error was: error while evaluating conditional: 'matrix_synapse_s3_media_store_enabled' is undefined

Updated: mautrix-signal to v0.3.0 & signald to 0.18.0

HOTFIX: matrix-registration-bot, fixed systemd template that caused setup error

This reverts commit a31017d716.