🔥 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/CountryFactory.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace Database\Factories;
+
+use App\Models\Country;
+use Illuminate\Database\Eloquent\Factories\Factory;
+
+/**
+ * @extends Factory<Country>
+ */
+class CountryFactory extends Factory
+{
+    /**
+     * @return array<string, mixed>
+     */
+    public function definition(): array
+    {
+        return [
+            'name' => fake()->unique()->country(),
+            'code' => strtoupper(fake()->unique()->lexify('??')),
+            'language_codes' => ['de'],
+        ];
+    }
+
+    public function germany(): static
+    {
+        return $this->state(fn () => [
+            'name' => 'Deutschland',
+            'code' => 'DE',
+            'language_codes' => ['de'],
+        ]);
+    }
+
+    public function austria(): static
+    {
+        return $this->state(fn () => [
+            'name' => 'Österreich',
+            'code' => 'AT',
+            'language_codes' => ['de'],
+        ]);
+    }
+
+    public function switzerland(): static
+    {
+        return $this->state(fn () => [
+            'name' => 'Schweiz',
+            'code' => 'CH',
+            'language_codes' => ['de', 'fr', 'it'],
+        ]);
+    }
+}