Bring back winter snow effect, gated by an admin setting

The site has flip-flopped on the snow effect every winter (add it,
remove it, repeat), meaning a PR round-trip each time. Instead, restore
the winter.js/is-land assets and gate them behind a new admin-toggleable
setting so the effect can be switched on/off from /admin/settings
without touching code.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0113BVPXDpEk9HPEqXvSG2WQ

app/Http/Controllers/Admin/SettingsController.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Controllers\Admin;
+
+use App\Http\Controllers\Controller;
+use App\Models\Setting;
+use Illuminate\Http\RedirectResponse;
+use Illuminate\Http\Request;
+use Illuminate\View\View;
+
+class SettingsController extends Controller
+{
+    public function show(): View
+    {
+        $settings = Setting::first();
+
+        return view('admin.settings.show', [
+            'settings' => $settings,
+        ]);
+    }
+
+    public function update(Request $request): RedirectResponse
+    {
+        $settings = Setting::firstOrNew();
+        $settings->winter_effect_enabled = $request->boolean('winter_effect_enabled');
+        $settings->save();
+
+        return redirect()->route('admin.settings.show');
+    }
+}

app/Models/Setting.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class Setting extends Model
+{
+    use HasFactory;
+
+    /**
+     * @var array<string, string>
+     */
+    protected $casts = [
+        'winter_effect_enabled' => 'boolean',
+    ];
+}

app/Providers/AppServiceProvider.php

@@ -2,10 +2,12 @@
 
 namespace App\Providers;
 
+use App\Models\Setting;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Pagination\LengthAwarePaginator;
 use Illuminate\Support\Collection;
 use Illuminate\Support\Facades\URL;
+use Illuminate\Support\Facades\View;
 use Illuminate\Support\ServiceProvider;
 use Symfony\Component\HtmlSanitizer\HtmlSanitizer;
 use Symfony\Component\HtmlSanitizer\HtmlSanitizerConfig;
@@ -63,5 +65,10 @@ class AppServiceProvider extends ServiceProvider
 
         // Force HTTPS URL generation in production
         URL::forceHttps($this->app->isProduction());
+
+        // Share whether the winter snow effect is enabled with the base layout
+        View::composer('master', function ($view) {
+            $view->with('winterEffectEnabled', Setting::first()?->winter_effect_enabled ?? false);
+        });
     }
 }