build(deploy)!: the instance's compose file is compose.learn.yaml, beside compose.train.yaml and compose.todo.yaml

No file has Compose's default name any more, so .env's COMPOSE_FILE is always set,
naming compose.learn.yaml first (.env.example sets it). compose.yaml stays as a link to
compose.learn.yaml for the one deploy that switches learn.halkyon.eu's .env over: the
deploy's merge runs with the COMPOSE_FILE from before. A later commit removes it.

BREAKING CHANGE: an instance's deploy/.env must set COMPOSE_FILE, starting with
compose.learn.yaml, before the link goes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_base_server/lib/src/common/network.dart

@@ -8,7 +8,7 @@ import 'package:serverpod/serverpod.dart';
 // checks and proofs of the recovery phrase). Behind a reverse proxy every connection comes from
 // the proxy, which would make each of those limits the whole instance's.
 // So for a connection from a proxy the operator trusts (`TRUSTED_PROXIES`;
-// deploy/compose.yaml names Caddy), the visitor is the last address of
+// deploy/compose.learn.yaml names Caddy), the visitor is the last address of
 // `X-Forwarded-For`: the one the proxy saw itself and added (Caddy replaces
 // what a visitor sends there unless that visitor is a proxy it trusts).
 // Never the `Forwarded` header, which Caddy passes on as the visitor wrote