feat(todo): the four tabs in Todo's frame, washed in strawberry, Settings from Browse

ADR 0033, step 1: go_router with a StatefulShellRoute and halkyon_ui's
NavigationFrame as Train's (D1), the tabs Today, Upcoming, Inbox and
Browse, each saying tasks come later (D2), every screen washing down in
strawberry (D3), and Settings over the tabs from Browse's cog, grouped in
cards: the operator's, the account, What's new and About Halkyon Todo,
the version below (D4). The account sheet and the empty home go.

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

@@ -8,11 +8,21 @@
 
   "instanceFirstStartSubtitle": "Choose the instance to keep your tasks on. Someone runs each one; you can add others later.",
 
-  "homeEmptyTitle": "Nothing here yet",
-  "homeEmptyHint": "Tasks come with a later version of Halkyon Todo.",
-
   "accountTitle": "Account",
   "accountDeleteMessage": "Your account is deleted on the server and on all your devices. This can't be undone.",
 
-  "aboutTitle": "About"
+  "aboutTitle": "About Halkyon Todo",
+
+  "shellTabToday": "Today",
+  "shellTabUpcoming": "Upcoming",
+  "shellTabInbox": "Inbox",
+  "shellTabBrowse": "Browse",
+  "todayLaterTitle": "Today's tasks come here",
+  "upcomingLaterTitle": "The days ahead come here",
+  "inboxLaterTitle": "Tasks without a project come here",
+  "browseLaterTitle": "Your projects and labels come here",
+  "tasksLaterHint": "Tasks come with a later version of Halkyon Todo.",
+  "settingsTitle": "Settings",
+  "settingsVersion": "Version {version} (build {build})",
+  "@settingsVersion": {"placeholders": {"version": {"type": "String"}, "build": {"type": "String"}}}
 }