feat(meditate): the app: Today, Explore, Profile, the sitting and its bells

halkyon_meditate_flutter on halkyon_app and halkyon_ui (ADR 0038): the
first start, sign-in and account as every Halkyon app's, a bar below
medium windows and a rail with the icon from medium on, fern washes,
Settings in cards (Sync, the operator's, Sitting, Practice, the
account, What's new, About, the version), English and German.

- Today: a greeting by the hour, Sit now at 5, 10, 20 minutes and the
  timer's own length, the practice of the day, the week with the days
  in a row, favourites, recently sat (D9).
- Explore: six practices of Halkyon's own, written for the app, found
  by a search without case or accents, by goal and by kind; each page
  with how it goes, its lengths, its heart and Start (D4, D10).
- The sitting, over the tabs: its time from the clock, a ring counting
  down, the cue of the moment, Pause and End, the bells at the start,
  between and at the end, the screen kept on; ended early, kept from a
  minute on where the person says so (D5, D6).
- Profile: every Halkyon app's, then the person's practice: minutes,
  sittings, days, the week and every sitting kept, to delete (D8).
- Settings and sittings sealed with the person's key and synced (D7).

The bells are synthesised by apps/meditate/tool/bells.py, the icon is
Lucide's sprout from cobalt through pacific into fern
(tool/app_icons.py). Releases and the deploy are a later step.

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

pubspec.yaml

@@ -15,6 +15,9 @@ workspace:
   - apps/learn/halkyon_learn_server
   - apps/learn/halkyon_learn_flutter
   - apps/learn/halkyon_learn_curator
+  - apps/meditate/halkyon_meditate_client
+  - apps/meditate/halkyon_meditate_server
+  - apps/meditate/halkyon_meditate_flutter
   - apps/todo/halkyon_todo_client
   - apps/todo/halkyon_todo_server
   - apps/todo/halkyon_todo_flutter