fix: Address code review findings for NotificationsView (FRE-4737)

- P0: Add default param to protocol list(params:) for compile fix
- P1: Fix onDelete async closure, implement deletion logic
- P2: Remove redundant objectWillChange.send() (Published handles it)
- P2: Make RelativeDateTimeFormatter static singleton (per-row perf)
- P3: Replace deprecated NavigationView with NavigationStack

Lendair/Views/NotificationRowView.swift

@@ -43,10 +43,14 @@ struct NotificationRowView: View {
     }
     
     private func formatTimestamp(_ date: Date) -> String {
+        Self.formatter.localizedString(for: date, relativeTo: Date())
+    }
+
+    private static let formatter: RelativeDateTimeFormatter = {
         let formatter = RelativeDateTimeFormatter()
         formatter.unitsStyle = .abbreviated
-        return formatter.localizedString(for: date, relativeTo: Date())
-    }
+        return formatter
+    }()
 }
 
 #Preview {