refactor(commodity-detail): optimize performance and fix UI flicker issues

1. add empty form tip for product message section
2. lazy load goods form to unblock initial page render
3. optimize category and tabbar rendering to fix flicker on WeChat mini-program
4. delay non-critical data processing to improve first-screen rendering speed
5. fix popup blank issue when opening product message form for the first time

common/js/goods_detail_base.js

@@ -185,9 +185,12 @@ export default {
 			if (this.goodsRoute != '/pages_goods/detail') this.setPublicShare();
 
 			// this.getBarrageData();
-			if (this.addonIsExist.form) {
-				await this.getGoodsForm();
-			}
+			// 性能优化: 商品表单(留言表单)仅在商品详情打开"立即留言"弹窗时才需要,
+			// 不再阻塞首次渲染。改为在后台并发请求, 用户真正打开弹窗时数据已就绪。
+			// 注意: 不再依赖 addonIsExist.form (后端可能未开启 form 插件, 但产品被设为"留言商品"(isinformation=2)
+			//       仍需展示留言表单), 始终尝试加载, getGoodsForm 内部已对失败分支兜底空数组。
+			this._goodsFormPromise = this.getGoodsForm();
+			// 不 await, 释放主流程; 调用方需要时可 await this._goodsFormPromise
 		},
 		/**
 		 * 刷新商品详情数据
@@ -327,14 +330,35 @@ export default {
 		 * 给 detail.vue 的 diy-form 直接消费。所有分支都做兜底初始化，避免下游拿到 undefined。
 		 */
 		async getGoodsForm() {
-			const res = await this.$api.sendRequest({
-				url: "/form/api/form/goodsform",
-				data: {
-					goods_id: this.goodsSkuDetail.goods_id,
-					format: 'object'
-				},
-				async: false
-			});
+			// 防御: sku 切换/数据未到时 goods_id 可能为 0/空, 此时直接走空数据分支,
+			// 避免后端拿到非法 goods_id 导致 4xx/5xx 后还把脏数据塞给前端。
+			if (!this.goodsSkuDetail || !this.goodsSkuDetail.goods_id) {
+				const emptyFn = () => {
+					this.$set(this.goodsSkuDetail, 'goods_form', []);
+					this.$set(this.goodsSkuDetail, 'goods_form_config', {});
+					this.$set(this.goodsSkuDetail, 'goods_form_name', '');
+					this.$set(this.goodsSkuDetail, 'goods_form_tip', '');
+					this.$set(this.goodsSkuDetail, 'goods_form_banner', '');
+					this.$set(this.goodsSkuDetail, 'goods_form_show_banner', false);
+					this.$set(this.goodsSkuDetail, 'goods_form_show_tip', false);
+				};
+				emptyFn();
+				return;
+			}
+			let res;
+			try {
+				res = await this.$api.sendRequest({
+					url: "/form/api/form/goodsform",
+					data: {
+						goods_id: this.goodsSkuDetail.goods_id,
+						format: 'object'
+					},
+					async: false
+				});
+			} catch (e) {
+				console.warn('getGoodsForm request failed', e);
+				res = null;
+			}
 			const empty = () => {
 				this.$set(this.goodsSkuDetail, 'goods_form', []);
 				this.$set(this.goodsSkuDetail, 'goods_form_config', {});