Fix: remove hardcoded Lucent nav item from CorePlugin

CorePlugin registered a "Lucent" navigation item pointing at /lucent
unconditionally, coupling the core package to a specific CMS that
consuming apps may not install.

src/CorePlugin.php

@@ -3,7 +3,6 @@
 namespace Modules\Core;
 
 use Filament\Contracts\Plugin;
-use Filament\Navigation\NavigationItem;
 use Filament\Panel;
 use Illuminate\Support\Facades\Mail;
 use Lunar\Admin\Filament\Resources\StaffResource;
@@ -26,14 +25,7 @@ class CorePlugin implements Plugin
             ->brandName('Boboko')
             ->brandLogo(asset('static/logos/core/boboko-logo.svg'))
             ->darkModeBrandLogo(asset('static/logos/core/boboko-logo-white.svg'))
-            ->login(Login::class)
-            ->navigationItems([
-                NavigationItem::make("Lucent")
-                    ->url("/lucent")
-                    ->icon("heroicon-o-sun")
-                    ->group("Content")
-                    ->sort(1),
-            ]);
+            ->login(Login::class);
 
         LunarPanel::extensions([
             StaffResource::class => StaffResourceExtension::class,