🔥 Add initial database migrations, seeders, and factories

🎨 Refactor `Lecturer` model to include new fields and factory usage
🔧 Update `DatabaseSeeder` to handle default seeds
🛠️ Enhance `einundzwanzig` database configuration for SQLite compatibility

database/factories/CategoryFactory.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace Database\Factories;
+
+use App\Models\Category;
+use Illuminate\Database\Eloquent\Factories\Factory;
+
+/**
+ * @extends Factory<Category>
+ */
+class CategoryFactory extends Factory
+{
+    /**
+     * @return array<string, mixed>
+     */
+    public function definition(): array
+    {
+        return [
+            'name' => fake()->unique()->randomElement([
+                'Grundlagen',
+                'Self Custody',
+                'Lightning',
+                'Nostr',
+                'Privacy',
+                'Mining',
+                'Wirtschaft',
+                'Recht',
+                'Technik',
+            ]),
+        ];
+    }
+}