feat: Implement order and invoice management, enhance addon features, and remove the 'Type' module.

app/Models/CartAddon.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Model;
+
+class CartAddon extends Model
+{
+    use HasFactory;
+
+    protected $table = 'cart_addons';
+
+    protected $fillable = [
+        'cart_id',
+        'addon_id',
+        'qty',
+        'price',
+    ];
+
+    /**
+     * Relationship: CartAddon belongs to Cart
+     */
+    public function cart()
+    {
+        return $this->belongsTo(Cart::class, 'cart_id');
+    }
+
+    /**
+     * Relationship: CartAddon belongs to Addon
+     */
+    public function addon()
+    {
+        return $this->belongsTo(Addon::class, 'addon_id');
+    }
+}