refactor(i18n): 扁平化所有国际化语言文件的翻译结构

移除多层嵌套的翻译对象，将所有翻译项直接挂载到顶层lang对象上，统一代码结构

lang/en-us/pay/cashier.js

@@ -1,21 +1,17 @@
 export const lang = {
-	pay: {
-		cashier: {
-			title: 'Cashier',
-			// Pay button
-			confirmPay: 'Confirm Payment',
-			// Empty states
-			noPayMethodConfigured: 'No payment method configured!',
-			orderAlreadyPaid: 'This order has been paid',
-			noPayInfo: 'Payment information not found',
-			// Payment methods
-			alipay: 'Alipay',
-			wechatpay: 'WeChat Pay',
-			// Messages
-			pleaseSelectPayMethod: 'Please select a payment method!',
-			paying: 'Processing payment...',
-			paymentCancelled: 'Payment cancelled',
-			paymentFailed: 'Payment failed, reason: {reason}',
-		}
-	}
+	title: 'Cashier',
+	// Pay button
+	confirmPay: 'Confirm Payment',
+	// Empty states
+	noPayMethodConfigured: 'No payment method configured!',
+	orderAlreadyPaid: 'This order has been paid',
+	noPayInfo: 'Payment information not found',
+	// Payment methods
+	alipay: 'Alipay',
+	wechatpay: 'WeChat Pay',
+	// Messages
+	pleaseSelectPayMethod: 'Please select a payment method!',
+	paying: 'Processing payment...',
+	paymentCancelled: 'Payment cancelled',
+	paymentFailed: 'Payment failed, reason: {reason}',
 };