Update translations for cascade meeting list notes

Add and update localization strings for the cascade meeting list, including a note about `cascadeListItem` being intentionally kept for backward compatibility.

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artifacts/tx-os/src/locales/ar.json

@@ -1345,6 +1345,7 @@
       "cascadeColMeetingNumber": "رقم الاجتماع",
       "cascadeColTitle": "العنوان",
       "cascadeColTimes": "من ← إلى",
+      "_cascadeListItemNote": "#480: cascadeListItem لم يعد يُستخدم (قائمة الاجتماعات المتأثرة أصبحت جدولاً)؛ احتُفظ به لتفادي تغييرات في أدوات أخرى قد تشير إليه.",
       "cascadeListItem": "{{title}} — {{oldStart}} ← {{newStart}}",
       "cascadeShift_zero": "تأجيل الاجتماعات اللاحقة",
       "cascadeShift_one": "تأجيل اجتماع واحد لاحق",

artifacts/tx-os/src/locales/en.json

@@ -1228,6 +1228,7 @@
       "cascadeColMeetingNumber": "Meeting #",
       "cascadeColTitle": "Title",
       "cascadeColTimes": "From → To",
+      "_cascadeListItemNote": "#480: cascadeListItem is no longer rendered (the affected-meetings list is now a table); kept to avoid churn for downstream tooling that may reference the key.",
       "cascadeListItem": "{{title}} — {{oldStart}} → {{newStart}}",
       "cascadeShift_one": "Shift {{count}} following meeting",
       "cascadeShift_other": "Shift {{count}} following meetings",