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>

packages/halkyon_ui/pubspec.yaml

@@ -1,45 +0,0 @@
-name: halkyon_ui
-description: "Halkyon's look, shared by its apps: the theme around cobalt and copper, the bundled Noto Sans, window sizes, and the widgets every app's screens are built of."
-version: 0.1.0
-publish_to: none
-resolution: workspace
-
-environment:
-  sdk: ^3.13.0
-  flutter: ^3.44.4
-
-dependencies:
-  # Material 3 Expressive's loading indicator, which Flutter doesn't ship yet
-  # (AppLoadingIndicator).
-  expressive_loading_indicator: ^0.0.1
-  flutter:
-    sdk: flutter
-  # gen-l10n's output imports it; apps take Material's texts from material_ui.
-  flutter_localizations:
-    sdk: flutter
-  intl: ^0.20.3
-  lucide_icons_flutter: ^3.1.20
-  material_ui: ^1.5.0
-
-dev_dependencies:
-  flutter_test:
-    sdk: flutter
-
-flutter:
-  # Generates HalkyonUiLocalizations from lib/l10n (see l10n.yaml).
-  generate: true
-
-  assets:
-    # Noto Sans's licence, for the licence list (registerFontLicenses).
-    - assets/fonts/OFL-NotoSans.txt
-
-  # Noto Sans for Latin, Greek (polytonic too) and Cyrillic, the same on every
-  # device and never fetched; each file holds every weight (variable fonts). An
-  # app reaches it as `packages/halkyon_ui/Noto Sans` (appFontFamily). The CJK
-  # fonts behind it are the apps' own to bundle (appFontFallback).
-  fonts:
-    - family: Noto Sans
-      fonts:
-        - asset: assets/fonts/NotoSans-Variable.ttf
-        - asset: assets/fonts/NotoSans-Italic-Variable.ttf
-          style: italic