feat(layout): Layout-Einstellungen, Dark-Mode, Logo, Hilfe-Menü

- Settings Key-Value Store (DB + Cache)
- Einstellungen → Layout: Seitenname, Logo, Button-Farbe, Dark/Light-Mode
- Hilfe-Menü (Ebene 0): Handbuch + Changelog im Browser
- Navigation erweitert: Einstellungen-Dropdown + Hilfe-Dropdown
- CHANGELOG v0.4.0

Version: 0.4.0

app/Providers/SettingsServiceProvider.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace App\Providers;
+
+use App\Services\SettingsService;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Support\Facades\View;
+use Illuminate\Support\ServiceProvider;
+
+class SettingsServiceProvider extends ServiceProvider
+{
+    public function register(): void
+    {
+        $this->app->singleton(SettingsService::class);
+    }
+
+    public function boot(): void
+    {
+        // Settings nur laden wenn die Tabelle existiert (z.B. vor Migration schützen)
+        if (!$this->app->runningInConsole() && Schema::hasTable('settings')) {
+            $settings = $this->app->make(SettingsService::class)->all();
+
+            View::share('appSettings', $settings);
+        } else {
+            View::share('appSettings', [
+                'site_name'    => config('app.name'),
+                'site_logo'    => '',
+                'button_color' => '#4f46e5',
+                'theme_mode'   => 'light',
+            ]);
+        }
+    }
+}