docs: 补充档案回流接口调用说明(docs/api.md + 前台 API 文档页)

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

public-frontend/src/components/ApiDocs.tsx

@@ -343,6 +343,41 @@ curl -H "Authorization: Bearer og_live_xxxxxxxx" ${BASE}/products/search?q=牛
 }`}
       />
 
+      <Endpoint
+        method="POST"
+        path="/api/public/backflow"
+        title="档案回流（批量回流未收录商品，需 API Key）"
+        desc="供进销存等机器调用方使用：把档案里尚未收录的商品批量推送过来，进入人工审核队列，审核通过后才收录。必须携带 API Key（与上文同一类 og_live_ 密钥），不会直接写入商品。请求体为商品对象数组（与公众投稿同结构），单次最多 1000 条；按条码 GTIN 逐条去重，返回每条结果：queued（入队待审）/ exists（已收录跳过）/ duplicate（已有同条码待审跳过）/ invalid（无效，如名称为空）。"
+        params={[
+          { name: "name", required: true, desc: "商品名称（数组中每个元素）" },
+          { name: "gtin", desc: "条码（GTIN），强烈建议提供，用于去重" },
+          { name: "brand_name", desc: "品牌名" },
+          { name: "category_id", desc: "品类编码，如 food.beverages" },
+          { name: "net_content_value / net_content_unit", desc: "净含量数值 / 单位" },
+          { name: "country_of_origin", desc: "产地" },
+          { name: "msrp", desc: "零售价快照数组，元素含 amount/currency/region/effective_date" },
+          { name: "note", desc: "备注" },
+        ]}
+        example={`curl -X POST ${ORIGIN}/api/public/backflow \\
+  -H "X-API-Key: og_live_xxxxxxxx" \\
+  -H "Content-Type: application/json" \\
+  -d '[
+    {"name":"某某牛奶 250ml","gtin":"6901234567890","brand_name":"某品牌",
+     "net_content_value":250,"net_content_unit":"ml",
+     "msrp":[{"amount":3.5,"currency":"CNY","region":"CN"}]},
+    {"name":"已收录商品","gtin":"5449000000996"}
+  ]'`}
+        response={`{
+  "total": 2, "queued": 1, "exists": 1, "duplicate": 0, "invalid": 0,
+  "results": [
+    { "gtin": "6901234567890", "name": "某某牛奶 250ml",
+      "status": "queued", "id": "<submission-id>" },
+    { "gtin": "5449000000996", "name": "已收录商品",
+      "status": "exists", "reason": "该条码商品已收录" }
+  ]
+}`}
+      />
+
       <Endpoint
         method="POST"
         path="/api/v1/register"