refactor(Notifications): further support for duplicate notification logic

- New setting to stack or suppress identical alerts (on by default)
Closes #2334

quickshell/translations/settings_search_index.json

@@ -5807,6 +5807,28 @@
     ],
     "description": "Use smaller notification cards"
   },
+  {
+    "section": "notificationDedupeEnabled",
+    "label": "Suppress Duplicate Notifications",
+    "tabIndex": 17,
+    "category": "Notifications",
+    "keywords": [
+      "alert",
+      "alerts",
+      "coalesce",
+      "dedupe",
+      "duplicate",
+      "duplicates",
+      "messages",
+      "notif",
+      "notification",
+      "notifications",
+      "repeat",
+      "stack",
+      "toast"
+    ],
+    "description": "Control whether identical alerts stack or show as a single popup"
+  },
   {
     "section": "notificationHistorySaveCritical",
     "label": "Critical Priority",