feat(nav): nest Calendar vizual under Calendar (Programări) in sidebar

CalendarBoard::getNavigationParentItem() now returns the Appointments
resource nav label so the sidebar collapses them into a single
expandable menu item. Routes and logic unchanged — both
/app/appointments and /app/calendar-board still work.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/Filament/Tenant/Pages/CalendarBoard.php

@@ -25,6 +25,15 @@ class CalendarBoard extends Page
         return __('nav.group.CRM');
     }
 
+    /**
+     * Nest this page under the "Calendar" (Programări) list resource so the
+     * two show up as a single expandable menu item in the sidebar.
+     */
+    public static function getNavigationParentItem(): ?string
+    {
+        return __('nav.label.Calendar');
+    }
+
     protected static ?int $navigationSort = 8;
 
     protected static ?string $title = null;