docs(login v2): update proxy examples (#10358)

# Which Problems Are Solved

- The proxy examples are updated so a self-hosted login container is
deployed.
- The proxies are configured to direct traffic at /ui/v2/login to it.

# How the Problems Are Solved

The base compose file is extended by correctly configured login
containers for all three scenarios
- TLS disabled
- External TLS
- TLS Enabled

The proxy always connects to the login via HTTP.

# Additional Changes

- All proxies have the TLS disabled mode outcommented, because the login
container has state problems, maybe because it needs secure cookies. The
need for this is unclear, so we avoid creating a follow-up issue.
- The httpd external mode is incommented, as gRPC connections work with
this configuration.
- *ZITADEL* is replaced by *Zitadel*

# Additional Context

- Partially Closes #10016

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>
(cherry picked from commit 4930870504)

docs/sidebars.js

@@ -1120,6 +1120,7 @@ module.exports = {
             "self-hosting/manage/reverseproxy/traefik/traefik",
             "self-hosting/manage/reverseproxy/nginx/nginx",
             "self-hosting/manage/reverseproxy/caddy/caddy",
+            "self-hosting/manage/reverseproxy/httpd/httpd",
             "self-hosting/manage/reverseproxy/cloudflare/cloudflare",
             "self-hosting/manage/reverseproxy/cloudflare_tunnel/cloudflare_tunnel",
             "self-hosting/manage/reverseproxy/zitadel_cloud/zitadel_cloud",