feat: 新增多语言文案并修复动态国际化调用问题

1. 新增多语言文件覆盖组件、页面、公共模块的翻译文案
2. 修复多处动态拼接lang key的调用，增加兜底逻辑避免空值或原始key暴露
3. 补全DIY组件、业务页面的国际化适配
4. 新增P2动态key国际化处理方案文档

common/js/goods_detail_base.js

@@ -141,7 +141,7 @@ export default {
 			});
 			this.goodsSkuDetail.swiperHeight = maxHeight + 'px';
 
-			this.goodsSkuDetail.unit = this.goodsSkuDetail.unit || "件";
+			this.goodsSkuDetail.unit = this.goodsSkuDetail.unit || this.$lang('unit.piece');
 
 			// 当前商品SKU规格
 			if (this.goodsSkuDetail.sku_spec_format) this.goodsSkuDetail.sku_spec_format = JSON.parse(this.goodsSkuDetail.sku_spec_format);
@@ -199,7 +199,7 @@ export default {
 			if (this.$refs.goodsDetailView) {
 
 				// 初始化商品详情视图数据
-				this.goodsSkuDetail.unit = this.goodsSkuDetail.unit || "件";
+				this.goodsSkuDetail.unit = this.goodsSkuDetail.unit || this.$lang('unit.piece');
 
 				// 解决轮播图数量不一致时，切换到第一个
 				if (this.swiperCurrent > this.goodsSkuDetail.sku_images.length) {