Nav: add Owner Ledger link under Finance → Receivables

The Owner Ledger page (/dashboard/owner-ledger) was a route with no menu
entry, so it was only reachable by URL. Add it to the Receivables group so
staff can reach it (and the new Add Note action).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/components/dashboard/DashboardTopNav.tsx

@@ -166,6 +166,7 @@ const megaMenuSections: MegaMenuSection[] = [
       {
         heading: "Receivables",
         items: [
+          { title: "Owner Ledger", url: "/dashboard/owner-ledger", icon: BookOpen },
           { title: "Outstanding Balances", url: "/dashboard/outstanding-balances", icon: DollarSign },
           { title: "Bulk Charges", url: "/dashboard/bulk-charges", icon: DollarSign },
           { title: "Collections", url: "/dashboard/collections", icon: DollarSign },