feat(todo): Today, Upcoming, Inbox, projects, quick add and the task sheet (ADR 0033, D8, D9)

The tabs hold the person's tasks: Today what is overdue (Reschedule
moving it all to a day, times kept) and what is due today; Upcoming the
overdue ones and the next four weeks day by day; Inbox and each
project's screen from Browse the tasks above and in their sections, done
ones on asking; Browse the projects with their open counts and the
labels. A task's row shows its check in its priority's colour, its date
in the colour of how near it is, its deadline, its sub-tasks done and
its labels; quick add takes its title, date, priority, project, labels
and description and stays for the next; its sheet edits all of it, adds
sub-tasks and deletes it with them after asking. Colours are the
palette's, cerise for overdue and P1 against the strawberry wash.

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

@@ -29,6 +29,9 @@ dependencies:
   # The device's half of signing in with OpenID Connect (ADR 0023): the
   # browser that SimpleLogin's sign-in opens, and on Linux and Windows the
   # loopback it comes back to, which the app builds with its name.
+  # Primitives every Halkyon package shares: `CoalescingRunner`.
+  halkyon_core:
+    path: ../../../packages/halkyon_core
   halkyon_oidc_flutter:
     path: ../../../packages/halkyon_oidc_flutter
   halkyon_todo_client: