feat(chat): UsageService for cost/token summarization

internal/chat/service_usage.go

@@ -0,0 +1,35 @@
+package chat
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+type usageService struct{ repo Repository }
+
+var _ UsageService = (*usageService)(nil)
+
+// NewUsageService 构造 llm_usage 写入与汇总查询服务。
+func NewUsageService(repo Repository) UsageService { return &usageService{repo: repo} }
+
+func (s *usageService) Insert(ctx context.Context, in UsageRecord) error {
+	return s.repo.InsertUsage(ctx, in)
+}
+
+func (s *usageService) SummarizeByUser(ctx context.Context, from, to time.Time) ([]UserUsageRow, error) {
+	return s.repo.SummarizeUsageByUser(ctx, from, to)
+}
+
+func (s *usageService) SummarizeByModel(ctx context.Context, from, to time.Time) ([]ModelUsageRow, error) {
+	return s.repo.SummarizeUsageByModel(ctx, from, to)
+}
+
+func (s *usageService) SummarizeByDay(ctx context.Context, from, to time.Time) ([]DayUsageRow, error) {
+	return s.repo.SummarizeUsageByDay(ctx, from, to)
+}
+
+func (s *usageService) UserDaily(ctx context.Context, userID uuid.UUID, from, to time.Time) ([]DayUsageRow, error) {
+	return s.repo.SummarizeUserDaily(ctx, userID, from, to)
+}