feat(todo): each project's Display: completed tasks, grouping, sorting and filters, synced (ADR 0033, D17)

- A Display button beside a project's menu (the Inbox's too), a dot
  on it while the project shows otherwise than at first, opens its
  sheet: completed tasks, grouping (date, deadline, added date,
  priority, label), sorting (name, date, deadline, added date,
  priority), filters by date, deadline, priority and label, and
  Reset all.
- The choices live in the project's sealed payload (ProjectView,
  written only once set), so every device shows the project alike.
- Grouped, the groups stand in the sections' place under pinned
  headings; rows are dragged only while sorted by hand by sections.
- Show done tasks moves from the menu into Display.

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_de.arb

@@ -14,8 +14,6 @@
   "settingsVersion": "Version {version} (Build {build})",
   "clear": "Entfernen",
   "colorLabel": "Farbe",
-  "completedShow": "Erledigte zeigen",
-  "completedHide": "Erledigte ausblenden",
   "dateTitle": "Datum",
   "dateNextWeek": "Nächste Woche",
   "dateWeekend": "Dieses Wochenende",
@@ -168,5 +166,41 @@
   "deadlineTitle": "Frist",
   "orderChanged": "Reihenfolge geändert",
   "addTaskCancel": "Hier ablegen zum Abbrechen",
-  "taskMovedTo": "Verschoben auf {day}"
+  "taskMovedTo": "Verschoben auf {day}",
+  "display": "Anzeige",
+  "displayCompleted": "Erledigte Aufgaben",
+  "displaySort": "Sortieren",
+  "displayGrouping": "Gruppierung",
+  "displaySorting": "Sortierung",
+  "displayFilter": "Filter",
+  "displayDeadline": "Frist",
+  "displayLabel": "Label",
+  "displayReset": "Alles zurücksetzen",
+  "displayDone": "Fertig",
+  "displayAll": "Alle",
+  "displayAny": "Beliebig",
+  "groupingNone": "Keine",
+  "groupingDate": "Datum",
+  "groupingDeadline": "Frist",
+  "groupingAdded": "Hinzugefügt am",
+  "groupingPriority": "Priorität",
+  "groupingLabel": "Label",
+  "sortingManual": "Manuell",
+  "sortingName": "Name",
+  "sortingDate": "Datum",
+  "sortingDeadline": "Frist",
+  "sortingAdded": "Hinzugefügt am",
+  "sortingPriority": "Priorität",
+  "rangeToday": "Heute",
+  "rangeThisWeek": "Diese Woche",
+  "rangeNext7": "Nächste 7 Tage",
+  "rangeThisMonth": "Dieser Monat",
+  "rangeNext30": "Nächste 30 Tage",
+  "rangeNoDate": "Kein Datum",
+  "rangeNoDeadline": "Keine Frist",
+  "viewNothingTitle": "Nichts passt",
+  "viewNothingHint": "Die Filter dieser Ansicht lassen hier jede Aufgabe aus. Unter Anzeige änderst du sie.",
+  "displaySave": "Speichern",
+  "displayCancel": "Abbrechen",
+  "groupNoLabel": "Ohne Label"
 }