feat(todo): dialogs on the desktop, the tabs reordered, a task's path and menu (ADR 0033, D11 to D14)

- halkyon_ui: showAdaptiveSheet shows a dialog on Linux, macOS and Windows
  at every width (bottom sheets stay on phones and tablets below expanded
  windows), so Learn and Train follow; SheetScaffold takes a heading in
  the title's place and may leave out its close button.
- Todo: the tabs are Inbox, Today, Upcoming, Browse, Today still opening;
  `serverpod start` launches the app on Linux, as it has no web build.
- A task's sheet shows where the task is (its project, an icon once tasks
  are above it, and the tasks above it, each opening what it names) and a
  ⋮ menu in place of its close button: when it was added (its UUID v7),
  Duplicate with its sub-tasks, hiding its done sub-tasks (synced in its
  payload), Close in the pane, Delete after asking. The description's icon
  stays by its first line.
- A row names its project and section at the end of its date's line; every
  menu entry has its icon.
- Learn: a studyset's path starts at the Library tab's icon, named by its
  tooltip.

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/lib/l10n/app_en.arb

@@ -167,5 +167,14 @@
   "searchNone": "Nothing found for “{query}”.",
   "@searchNone": {"placeholders": {"query": {"type": "String"}}},
   "searchProjects": "Projects",
-  "searchTasks": "Tasks"
+  "searchTasks": "Tasks",
+  "taskMore": "Task options",
+  "taskAddedOn": "Added on {when}",
+  "@taskAddedOn": {"placeholders": {"when": {"type": "String"}}},
+  "taskDuplicate": "Duplicate",
+  "taskDuplicated": "Task duplicated",
+  "subTasksHideDone": "Hide done sub-tasks",
+  "subTasksShowDone": "Show done sub-tasks",
+  "taskClose": "Close",
+  "taskPath": "Where the task is"
 }