docs(self-hosting): simplify lb example and replace compose example (#9844)

# Which Problems Are Solved

The load balancing compose example uses a dedicated service
`use-new-login` that gives the set up machine user the login role and
requires the v2 login using an instance feature. This is cumbersome and
unnecessary.

# How the Problems Are Solved

- A login client machine user is set up and the token is passed to the
login by using the environment variable ZITADEL_SERVICE_USER_TOKEN_FILE.
- The unnecessary service is removed

# Additional Changes

- Uses the static `MasterkeyNeedsToHave32Characters` master key.
- The load balancing example replaces the previous Docker Compose
example.
- The login uses `network_mode: service:zitadel` so it can access the
zitadel service in the docker network via localhost.
- Uses the docker provider for Traefik.

# Additional Context

- Complements https://github.com/zitadel/zitadel/pull/9496
- Partially closes https://github.com/zitadel/zitadel/issues/10016
- When we release, we should update the image tags to latest, for
example with [this PR](https://github.com/zitadel/zitadel/pull/10249).

---------

Co-authored-by: Tim Möhlmann <tim+github@zitadel.com>

docs/sidebars.js

@@ -1084,7 +1084,6 @@ module.exports = {
         "self-hosting/deploy/devcontainer",
         "self-hosting/deploy/knative",
         "self-hosting/deploy/kubernetes",
-        "self-hosting/deploy/loadbalancing-example/loadbalancing-example",
         "self-hosting/deploy/troubleshooting/troubleshooting",
       ],
     },