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

database/migrations/2026_06_29_000001_create_settings_table.php

@@ -0,0 +1,23 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('settings', function (Blueprint $table) {
+            $table->id();
+            $table->string('key')->unique();
+            $table->text('value')->nullable();
+            $table->timestamps();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('settings');
+    }
+};

database/seeders/DatabaseSeeder.php

@@ -10,6 +10,7 @@ class DatabaseSeeder extends Seeder
     {
         $this->call([
             RolesAndPermissionsSeeder::class,
+            SettingsSeeder::class,
         ]);
     }
 }

database/seeders/SettingsSeeder.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace Database\Seeders;
+
+use App\Models\Setting;
+use Illuminate\Database\Seeder;
+
+class SettingsSeeder extends Seeder
+{
+    public function run(): void
+    {
+        $defaults = [
+            'site_name'      => 'Network-MGMT',
+            'site_logo'      => '',
+            'button_color'   => '#4f46e5',  // Indigo-600
+            'theme_mode'     => 'light',    // light | dark
+        ];
+
+        foreach ($defaults as $key => $value) {
+            Setting::firstOrCreate(['key' => $key], ['value' => $value]);
+        }
+
+        $this->command->info('Default settings seeded.');
+    }
+}