feat(todo): rows in rounded boxes, Today as Todoist's, lists pulled to sync, a project's own colour

From the developer's review of 3 Nov 2026 (ADR 0033, D19 to D21):
- Today's tab shows today's day in its calendar, Browse the menu's lines,
  Display's button Lucide's square-menu.
- A task's row stands in a rounded box, the rows of a list a group rounded
  at its ends; the box is the row's own surface, so a chosen row's colour no
  longer shows under Upcoming's pinned week strip as the list scrolls. Its
  project and section end the line of its date at the row's right edge.
- Today has at most two groups: what is overdue, folding under its heading,
  and today's, headed "Tuesday, 3 Nov" ("Dienstag, 3. Nov."), without a
  "· Today" after it; Upcoming's days take the same form.
- Upcoming's way back to today shows whenever another day is picked.
- Today, Upcoming, the Inbox and every project pulled down sync now, an
  empty list too, as Learn's.
- A project's screen washes in its own colour, as a studyset's in Learn.
- "Add section" in place of "New section".

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_localizations.dart

@@ -463,7 +463,7 @@ abstract class AppLocalizations {
   /// No description provided for @sectionAdd.
   ///
   /// In en, this message translates to:
-  /// **'New section'**
+  /// **'Add section'**
   String get sectionAdd;
 
   /// No description provided for @sectionEdit.
@@ -1563,6 +1563,24 @@ abstract class AppLocalizations {
   /// In en, this message translates to:
   /// **'{count} more'**
   String monthMore(int count);
+
+  /// intl's DateFormat pattern of a day's heading in Today and Upcoming, as Todoist's ("Tuesday, 3 Nov"): EEEE the weekday, d the day, MMM the short month.
+  ///
+  /// In en, this message translates to:
+  /// **'EEEE, d MMM'**
+  String get dayHeadingPattern;
+
+  /// No description provided for @overdueHide.
+  ///
+  /// In en, this message translates to:
+  /// **'Hide what is overdue'**
+  String get overdueHide;
+
+  /// No description provided for @overdueShow.
+  ///
+  /// In en, this message translates to:
+  /// **'Show what is overdue'**
+  String get overdueShow;
 }
 
 class _AppLocalizationsDelegate