feat: 新增租戶品牌客製化系統（Logo、主色系）、修正 hardcoded 顏色為 CSS 變數

resources/js/Pages/PurchaseOrder/Create.tsx

@@ -174,7 +174,7 @@ export default function CreatePurchaseOrder({
 
                     <div className="mb-6">
                         <h1 className="text-2xl font-bold text-grey-0 flex items-center gap-2">
-                            <ShoppingCart className="h-6 w-6 text-[#01ab83]" />
+                            <ShoppingCart className="h-6 w-6 text-primary-main" />
                             {order ? "編輯採購單" : "建立採購單"}
                         </h1>
                         <p className="text-gray-500 mt-1">

resources/js/Pages/PurchaseOrder/Index.tsx

@@ -109,7 +109,7 @@ export default function PurchaseOrderIndex({ orders, filters, warehouses }: Prop
                 <div className="flex items-center justify-between mb-6">
                     <div>
                         <h1 className="text-2xl font-bold text-grey-0 flex items-center gap-2">
-                            <ShoppingCart className="h-6 w-6 text-[#01ab83]" />
+                            <ShoppingCart className="h-6 w-6 text-primary-main" />
                             採購單管理
                         </h1>
                         <p className="text-gray-500 mt-1">

resources/js/Pages/PurchaseOrder/Show.tsx

@@ -38,7 +38,7 @@ export default function ViewPurchaseOrderPage({ order }: Props) {
                     <div className="flex items-center justify-between mb-6">
                         <div>
                             <h1 className="text-2xl font-bold text-grey-0 flex items-center gap-2">
-                                <ShoppingCart className="h-6 w-6 text-[#01ab83]" />
+                                <ShoppingCart className="h-6 w-6 text-primary-main" />
                                 查看採購單
                             </h1>
                             <p className="text-gray-500 mt-1">單號：{order.poNumber}</p>