feat(todo): tasks chosen together, quick add reading what is typed (ADR 0033, D14, D15)

- A section's heading stays atop a project's list while its tasks
  scroll beneath it (slivers, PinnedHeaderSliver).
- Upcoming's month unfolds in place beneath its strip, from its name
  or its handle; a button beside the month goes back to today.
- Tasks are chosen together: a row swiped right or held, or Select
  tasks in Today's, Upcoming's and a project's menu; a bar of date,
  move, labels, priority and more (complete, duplicate, deadline,
  delete) takes the navigation bar's place. A row swiped left asks
  for its date.
- TaskRepository.move moves tasks with their sub-tasks.
- parseQuickAdd reads #project, @label (an unknown one made),
  {deadline}, !!1 and p1 to p4, !30m, dates, times and recurrences
  (tomorrow 9am, Mon 18:00, ev Tue 7pm, every 2 days, every weekday),
  from a table of words per language: English, and German beside it.
- Each token is highlighted and shown on its chip; a tap keeps it as
  text, and a chip picked takes it out of the title.
- Quick add shows its title alone at first, its chips once typing
  starts, and the description and deadline behind its + (the
  description also from the down arrow).

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/todo/halkyon_todo_flutter/pubspec.yaml

@@ -67,6 +67,7 @@ dev_dependencies:
   flutter_test:
     sdk: flutter
 
+  test: any
 flutter:
   # Generates AppLocalizations from lib/l10n (see l10n.yaml).
   generate: true