feat(阶段三): 添加知识库模型和迁移

- 创建 knowledge_bases 表迁移
- 创建 KnowledgeBase 模型
- 创建 KnowledgeBaseFactory 工厂类
- 支持与终端的多对多关联关系

database/factories/KnowledgeBaseFactory.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace Database\Factories;
+
+use App\Models\KnowledgeBase;
+use Illuminate\Database\Eloquent\Factories\Factory;
+
+/**
+ * @extends \Illuminate\Database\Eloquent\Factories\Factory<\App\Models\KnowledgeBase>
+ */
+class KnowledgeBaseFactory extends Factory
+{
+    protected $model = KnowledgeBase::class;
+
+    /**
+     * Define the model's default state.
+     *
+     * @return array<string, mixed>
+     */
+    public function definition(): array
+    {
+        return [
+            'name' => $this->faker->words(3, true),
+            'description' => $this->faker->sentence(),
+            'status' => $this->faker->randomElement(['active', 'inactive']),
+        ];
+    }
+
+    /**
+     * 指定知识库为激活状态
+     */
+    public function active(): static
+    {
+        return $this->state(fn (array $attributes) => [
+            'status' => 'active',
+        ]);
+    }
+
+    /**
+     * 指定知识库为非激活状态
+     */
+    public function inactive(): static
+    {
+        return $this->state(fn (array $attributes) => [
+            'status' => 'inactive',
+        ]);
+    }
+}