fix(pl): keep multi-brand site feedback when plan product row is stale

Persist submitted brand qtys even if plan brand_mode lookup fails; resolve soft-deleted plan products for brand metadata instead of substituting another product; stop seeding all actual qty onto the first brand option.

Co-authored-by: Cursor <cursoragent@cursor.com>

web-admin/src/components/business/brand-qty-chips-field/index.vue

@@ -201,27 +201,7 @@
     setQty(brandId, normalized)
   }
 
-  watch(
-    () => [props.brandMode, props.requiredBrandId, props.brandOptions] as const,
-    () => {
-      if (props.brandMode !== 'required') return
-      const id = props.requiredBrandId || props.brandOptions[0]?.brandId
-      if (!id) return
-      const opt = props.brandOptions.find((o) => o.brandId === id)
-      const existing = props.modelValue.find((r) => r.brandId === id)
-      if (!existing) {
-        emitRows([
-          ...props.modelValue,
-          {
-            brandId: id,
-            brandName: opt?.brandName || '指定品牌',
-            qty: 0
-          }
-        ])
-      }
-    },
-    { immediate: true }
-  )
+  // 偏好品牌预选由父级初始化；组件内不再强制回填，避免取消后被再次插入
 </script>
 
 <style scoped lang="scss">