refactor!: packages, paths and app IDs under Halkyon Days' names (ADR 0045, step 3)

Learn's folder is apps/halkyon, Todo's apps/myrmex; every package of
ours takes the prefix halkyone_ (halkyone_halkyon_*, halkyone_myrmex_*,
halkyone_train_*, halkyone_meditate_*, halkyone_app, halkyone_base_* and
the other shared ones; halkyon_oidc_* keeps its name, D11). Halkyon and
Myrmex take the app IDs one.halky.halkyon and one.halky.myrmex (D10);
Train and Meditate keep theirs, while every app's Android namespace,
Kotlin package and method channels move to one.halky. The snaps are
halkyon and myrmex (D17), each built in a clone with its recipe in
place of snap/, as Train's and Todo's were.

Serverpod finds a database's migrations by its module's name, which
changed with the packages':
- each server's new, empty migration ("rename") records itself under
  the new names and deletes the rows under the old ones;
- deploy/redeploy.sh copies each database's record to the new name
  before the migrations (carry_module), so the renamed servers find
  their databases migrated; a copy, never a move, so a deploy failing
  before the migration commits leaves the old rows in place;
- Train and Meditate keep their devices' databases: halkyone_app's
  carryMigrationRecord copies their record before the sync engine
  opens them (openPersonDatabase);
- the client migrations' generated moduleName getters, one line each,
  say the new names: Serverpod's client asserts in debug builds that
  every migration names the module, and create-migration never writes
  a migration's files again.

Train's WorkManager work is enqueued under new names, the former ones
cancelled: the work kept names the workers' former classes.

The release tool: an app's tags of its earlier names count as its
history (legacyTagPrefixes), the shared packages' former paths count
for its version, and every snap is built in a clone (atRoot gone).

The databases, Docker images and Compose project keep their names
until step 5.

BREAKING CHANGE: Halkyon (Learn) and Myrmex (Todo) are new apps to
Android and the Snap Store: installs of app.halkyon.learn and
app.halkyon.todo don't update to them.

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/train/halkyon_train_client/lib/migrations/migration_registry.dart

@@ -1,45 +0,0 @@
-/// AUTOGENERATED BY SERVERPOD create-migration - DO NOT EDIT BY HAND
-/// Merging: resolve registry conflicts the same as migration_registry.txt.
-library;
-
-import 'package:serverpod_database/serverpod_database.dart';
-
-part '20261028101012641-workouts/migration.dart';
-part '20261028164640000-profile/migration.dart';
-part '20261028181405893-days/migration.dart';
-part '20261028211508606-plans/migration.dart';
-part '20261028231042668-routes/migration.dart';
-part '20261102103211357-training-places/migration.dart';
-part '20261102113104496-strength-plans/migration.dart';
-part '20261103204323683-body-weights/migration.dart';
-part '20261110225636220-file-store/migration.dart';
-part '20261111091721828-shared-spaces/migration.dart';
-part '20261111100125761-shared-space-keys/migration.dart';
-part '20261111145610490-shared-space-key-roll/migration.dart';
-part '20261111170121936-shared-space-invitations/migration.dart';
-part '20261111182840467-agents/migration.dart';
-
-/// Migration registry for the client-side database.
-class MigrationRegistry {
-  /// Ordered list of all client-side database migrations.
-  /// New migrations are always appended at the end.
-  static final List<MigrationVersionSql> migrations = [
-    _Migration20261028101012641_workouts(),
-    _Migration20261028164640000_profile(),
-    _Migration20261028181405893_days(),
-    _Migration20261028211508606_plans(),
-    _Migration20261028231042668_routes(),
-    _Migration20261102103211357_training_places(),
-    _Migration20261102113104496_strength_plans(),
-    _Migration20261103204323683_body_weights(),
-    _Migration20261110225636220_file_store(),
-    _Migration20261111091721828_shared_spaces(),
-    _Migration20261111100125761_shared_space_keys(),
-    _Migration20261111145610490_shared_space_key_roll(),
-    _Migration20261111170121936_shared_space_invitations(),
-    _Migration20261111182840467_agents(),
-  ];
-
-  /// List of all client-side database migration versions.
-  static List<String> get versions => migrations.map((m) => m.version).toList();
-}