feat(admin): add /api/import/bypos endpoint for bypos-collector import

Brings the bypos JSONL import backend (handler + store) into main so the
bypos-collector tool's import feature works end-to-end. Records are upserted
on GTIN with manufacturer/MSRP/barcode/source provenance, quality recomputed
per product. Only status=hit records with a name are imported.

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

api/internal/adminhandler/handler.go

@@ -90,6 +90,8 @@ func (h *Handler) Router() http.Handler {
 			r.Put("/api/categories/{id}", h.UpdateCategory)
 			r.Delete("/api/categories/{id}", h.DeleteCategory)
 
+			r.Post("/api/import/bypos", h.ImportBypos)
+
 			r.Get("/api/submissions", h.ListSubmissions)
 			r.Get("/api/submissions/{id}", h.GetSubmission)
 			r.Post("/api/submissions/{id}/approve", h.ApproveSubmission)

api/internal/adminhandler/import_bypos.go

@@ -0,0 +1,30 @@
+package adminhandler
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/baicai2026-baicai/goods/api/internal/adminstore"
+)
+
+func (h *Handler) ImportBypos(w http.ResponseWriter, r *http.Request) {
+	var records []adminstore.ByposRecord
+	dec := json.NewDecoder(http.MaxBytesReader(w, r.Body, 50<<20))
+	for dec.More() {
+		var rec adminstore.ByposRecord
+		if err := dec.Decode(&rec); err != nil {
+			continue
+		}
+		records = append(records, rec)
+	}
+	if len(records) == 0 {
+		writeError(w, http.StatusBadRequest, "empty", "\u6ca1\u6709\u53ef\u5bfc\u5165\u7684\u8bb0\u5f55")
+		return
+	}
+	result, err := h.store.ImportByposRecords(r.Context(), records)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "import_error", err.Error())
+		return
+	}
+	writeJSON(w, http.StatusOK, result)
+}