feat(todo): comments on a task (ADR 0033, D36)

Plain text with links, written, edited and deleted in the task's sheet,
counted on its row. They are sealed in `task_comment`, the task they belong
to with them, and go with their task.

Whats-New: Comments: write on a task, edit or delete what you wrote, and open its links.
Whats-New-De: Kommentare: Schreibe zu einer Aufgabe, bearbeite oder lösche es und öffne Links darin.

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

@@ -55,6 +55,15 @@
   "filterMatches": "{count, plural, =1{1 Aufgabe passt} other{{count} Aufgaben passen}}",
   "filterNotRead": "Nicht verstanden bei „{near}“",
   "filterNotReadEnd": "Die Abfrage endet zu früh",
+  "commentsTitle": "Kommentare",
+  "commentAdd": "Kommentar schreiben",
+  "commentSend": "Kommentar senden",
+  "commentMenu": "Kommentarmenü",
+  "commentEdit": "Kommentar bearbeiten",
+  "commentCopy": "Text kopieren",
+  "commentDelete": "Kommentar löschen",
+  "commentDeleteTitle": "Kommentar löschen?",
+  "commentEdited": "{when}, bearbeitet",
   "labelsTitle": "Labels",
   "labelsNone": "Noch keine Labels.",
   "labelsNoneSet": "Keine Labels",