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>

apps/learn/halkyon_learn_server/README.md

@@ -26,12 +26,12 @@ EDRDG's licence asks a server showing its dictionaries to update them at least
 once a month:
 
 - **An instance** keeps them current by itself: the `dictionaries` service in
-  `deploy/compose.yaml` (the curator, in a container of its own) downloads
+  `deploy/compose.learn.yaml` (the curator, in a container of its own) downloads
   EDRDG's files of the day once its files are a week old, converts them, and
   replaces them in a volume the server reads (`curate update`, the curator's
   README); the server takes them up within the hour. To supply files yourself
   instead, remove the service and mount `deploy/dictionaries/` into the server
-  (`compose.yaml` says how), and update them monthly.
+  (`compose.learn.yaml` says how), and update them monthly.
 - **Development:** `dart run halkyon_learn_curator:curate update --into
   ../halkyon_learn_server/dictionaries` in the curator's folder (about a
   minute); the server takes them up within the hour.

apps/learn/halkyon_learn_server/config/production.yaml

@@ -25,7 +25,7 @@ webServer:
   publicPort: 443
   publicScheme: https
 
-# The database: the `postgres` service of deploy/compose.yaml, reachable only inside
+# The database: the `postgres` service of deploy/compose.learn.yaml, reachable only inside
 # the Compose network (it publishes no port), so no TLS between server and database.
 # The password comes from the environment (SERVERPOD_DATABASE_PASSWORD, set in
 # deploy/.env); there is no production passwords.yaml.

apps/learn/halkyon_learn_server/lib/src/dictionary/dictionary_reload_future_call.dart

@@ -3,7 +3,7 @@ import 'package:halkyon_learn_server/src/dictionary/dictionary_loader.dart';
 import 'package:serverpod/serverpod.dart';
 
 /// Rereads the dictionary folder and loads the files that changed: the
-/// dictionaries service replaces them weekly (`deploy/compose.yaml`); the
+/// dictionaries service replaces them weekly (`deploy/compose.learn.yaml`); the
 /// server schedules it hourly when it starts (`server.dart`): an hour
 /// with nothing changed costs it a hash of each file.
 class DictionaryReloadFutureCall extends FutureCall {