feat(mall): restore real brand and sales facets

Wave 6, the last substantive piece of the mock-API migration. Wave 1 removed the
brand facet and the sales/comments sorts for want of a model; sales turn out to
be derivable from order_items and a brand model is a table plus a column.

- a `brands` table with a nullable `products.brand_id` and an ordered admin
  replace, mirroring categories and storefront content; a public `GET /api/brands`
  and a `brand_id` filter on the catalog, which the search page's facet uses
- `sold_count` per product, computed from `order_items` joined to orders that
  reached payment, so an abandoned or cancelled checkout cannot count as a sale.
  It is computed per read rather than stored, so it cannot drift from the orders
  that produced it
- `sort=sales` alongside `sort=price`; anything else is still a 400
- merchants can set a product's brand through the existing product upsert
- the review UI is gone: the card's review figure and the product detail page's
  reviews tab, summary and replies. There is no reviews model, and the mall
  attributed invented comments to named shoppers and showed a "good rate". The
  now-unreferenced fabrication helpers went with it (`salesOf`, `commentCountOf`,
  `commentsFor`, `commentStats`, `salesRankFor`, `productDetail`, `storeDetail`)

Two bugs found by checking rather than trusting: the fixed-data `listProducts`
had silently ignored `brand_id`, `sort` and `order`, so the restored facet
rendered but filtered nothing until the rollback check caught it; and the seed's
brand lookup read back through the shared `r` variable the product loop
reassigns, working once and then throwing.

Verified: 29 backend tests green including a new brand-and-sales case; all three
frontends build; searching filters by brand (24 to 6) and sorts by sales with
counts matching the API; a product page offers detail and after-sale tabs only,
with a real sold count; the fixed-data rollback filters by brand too.

OpenSpec change: openspec/changes/replace-mock-api-wave-6

apps/mall/pages/goods/[id].vue

@@ -2,7 +2,7 @@
 import { t as pick } from "@vmall/shared";
 import { ApiError } from "@vmall/shared";
 import type { Category, Product, Sku } from "@vmall/shared";
-import { MOCK_COUPONS, commentStats, commentsFor, salesOf } from "~/mock/data";
+import { MOCK_COUPONS } from "~/mock/data";
 import { lowestSku } from "~/utils/product";
 import { useCartStore } from "~/stores/cart";
 
@@ -27,8 +27,8 @@ const { data: pageData } = await useAsyncData(
     const current = await $api.getProduct(routeId.value);
     // The rail uses live catalogue products so its links resolve; the store
     // card, comments and coupons stay local display-only content (non-goals).
-    // Store best sellers, mirroring the mock's salesRankFor(shopId). Ranking by
-    // category would empty the rail for any product alone in its leaf category.
+    // Store best sellers, ranking the shop's own products. Ranking by category
+    // would empty the rail for any product alone in its leaf category.
     const siblings = await $api.listProducts({
       shop_id: current.shop_id,
       per_page: 6,
@@ -54,15 +54,11 @@ const detail = computed(() => {
     product: current,
     // Null when the shop has no public profile; the card is then not rendered.
     store: shops.value.find((shop) => shop.id === current.shop_id) ?? null,
-    comments: commentsFor(current.id),
-    commentStats: commentStats(current.id),
     coupons: MOCK_COUPONS,
     salesRank: related.value,
   };
 });
 
-/// Display-only sales figure; `salesOf` hashes the id so it is safe for UUIDs.
-
 const store = computed(() => detail.value?.store ?? null);
 const selectedAttributes = reactive<Record<string, string>>({});
 const quantity = ref(1);
@@ -174,9 +170,10 @@ const addCart = async (): Promise<void> => {
   }
 };
 
+// No reviews tab: there is no reviews capability, and the mall will not present
+// invented reviewers and ratings as fact. See the wave-6 design.
 const tabs = computed(() => [
   { key: "detail", label: t("product.tabsDetail") },
-  { key: "reviews", label: t("product.tabsReviews") },
   { key: "service", label: t("product.tabsAfterSale") },
 ]);
 
@@ -242,8 +239,7 @@ const detailImages = computed(() => product.value?.images ?? []);
             <span v-if="matchedSku" class="market-label">{{ t("product.marketPrice") }} <s><PriceText :amount-minor="marketPrice" :currency="matchedSku.currency" /></s></span>
           </div>
           <div class="summary-meta">
-            <span>{{ t("product.sold", { n: salesOf(detail.product) }) }}</span>
-            <span>{{ t("product.commentCount", { n: detail.commentStats.all }) }}</span>
+            <span>{{ t("product.sold", { n: detail.product.sold_count }) }}</span>
             <span :class="{ soldout: stock <= 0 }">{{ stock > 0 ? t("product.stock", { n: stock }) : t("product.noStock") }}</span>
           </div>
 
@@ -324,20 +320,6 @@ const detailImages = computed(() => product.value?.images ?? []);
                 <p>{{ pick(detail.product.description, locale) }}</p>
                 <img v-for="(image, index) in detailImages" :key="`${image}-detail-${index}`" :src="image" :alt="t('product.detail')" loading="lazy" />
               </div>
-              <div v-else-if="active === 'reviews'" class="reviews-content">
-                <div class="review-summary">
-                  <strong>{{ t("product.reviewSummary", { rate: detail.commentStats.goodRate, n: detail.commentStats.all }) }}</strong>
-                  <span>{{ t("product.reviewAll") }}</span>
-                </div>
-                <article v-for="comment in detail.comments" :key="comment.id" class="review">
-                  <img :src="comment.avatar" :alt="comment.author" loading="lazy" />
-                  <div class="review-body">
-                    <header><strong>{{ comment.author }}</strong><UiRatingStars :value="comment.rating" :size="13" /><time>{{ comment.createdAt }}</time></header>
-                    <p>{{ pick(comment.content, locale) }}</p>
-                    <div v-if="comment.reply" class="reply"><strong>{{ t("product.reply") }}:</strong> {{ pick(comment.reply, locale) }}</div>
-                  </div>
-                </article>
-              </div>
               <div v-else class="service-content">
                 <h2>{{ t("product.tabsAfterSale") }}</h2>
                 <p v-if="detail.store?.after_sale">{{ pick(detail.store.after_sale, locale) }}</p>