feat: 数据概览/操作日志/批量操作 + 首页合格档案数

后台新增「数据概览」(商品/合格/按状态/品牌/分类/待审核) 与「操作日志」(全局审计分页)；商品列表支持多选批量改状态/分类。公开首页标题改为「天工」并展示合格档案数；新增公开接口 /api/v1/stats 与后台 /api/stats、/api/audit、/api/products/bulk。合格口径=quality_score≥0.6 且在用。

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

api/internal/adminstore/stats.go

@@ -0,0 +1,61 @@
+package adminstore
+
+import "context"
+
+// QualifiedMinScore is the quality_score threshold at or above which a product
+// counts as "qualified" (合格) in admin and public stats.
+const QualifiedMinScore = 0.6
+
+// AdminStats summarizes the catalog for the admin overview dashboard.
+type AdminStats struct {
+	Products   int            `json:"products"`
+	Qualified  int            `json:"qualified"`
+	MinScore   float64        `json:"min_score"`
+	ByStatus   map[string]int `json:"by_status"`
+	Brands     int            `json:"brands"`
+	Categories int            `json:"categories"`
+	Pending    int            `json:"pending_submissions"`
+	AvgQuality float64        `json:"avg_quality"`
+}
+
+// Stats gathers the dashboard counters in a handful of aggregate queries.
+func (s *Store) Stats(ctx context.Context) (*AdminStats, error) {
+	out := &AdminStats{MinScore: QualifiedMinScore, ByStatus: map[string]int{}}
+
+	if err := s.pool.QueryRow(ctx, `
+SELECT count(*),
+       count(*) FILTER (WHERE quality_score >= $1 AND status = 'active'),
+       COALESCE(avg(quality_score), 0)
+FROM product`, QualifiedMinScore).Scan(&out.Products, &out.Qualified, &out.AvgQuality); err != nil {
+		return nil, err
+	}
+
+	rows, err := s.pool.Query(ctx, "SELECT status, count(*) FROM product GROUP BY status")
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var st string
+		var n int
+		if err := rows.Scan(&st, &n); err != nil {
+			return nil, err
+		}
+		out.ByStatus[st] = n
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+
+	if err := s.pool.QueryRow(ctx, "SELECT count(*) FROM brand").Scan(&out.Brands); err != nil {
+		return nil, err
+	}
+	if err := s.pool.QueryRow(ctx, "SELECT count(*) FROM category").Scan(&out.Categories); err != nil {
+		return nil, err
+	}
+	if err := s.pool.QueryRow(ctx,
+		"SELECT count(*) FROM submission WHERE status = 'pending'").Scan(&out.Pending); err != nil {
+		return nil, err
+	}
+	return out, nil
+}