feat(backend): add job metrics

backend/internal/repository/job_repository.go

@@ -5,6 +5,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"fmt"
+	"time"
 
 	"gitea.d3m0k1d.ru/d3m0k1d/HellreigN/backend/internal/models"
 	"gitea.d3m0k1d.ru/d3m0k1d/HellreigN/backend/internal/storage"
@@ -103,3 +104,29 @@ func (r *JobRepository) GetJobByID(ctx context.Context, jid int64) (models.Job,
 	job.Stdin = stdinVal
 	return job, nil
 }
+
+type JobMetrics struct {
+	Total     int
+	Success   int
+	Failed    int
+	Pending   int
+}
+
+// GetJobMetrics returns job success metrics for jobs updated since the given time.
+// A successful job has status == 0, failed has status != 0, pending has status == 0 with empty stdout/stderr.
+func (r *JobRepository) GetJobMetrics(ctx context.Context, since time.Time) (JobMetrics, error) {
+	var m JobMetrics
+	err := r.DB.QueryRowContext(ctx,
+		`SELECT
+			COUNT(*),
+			SUM(CASE WHEN status = 0 AND (stdout != '' OR stderr != '') THEN 1 ELSE 0 END),
+			SUM(CASE WHEN status != 0 THEN 1 ELSE 0 END),
+			SUM(CASE WHEN status = 0 AND stdout = '' AND stderr = '' THEN 1 ELSE 0 END)
+		FROM jobs WHERE updated_at >= ?`,
+		since,
+	).Scan(&m.Total, &m.Success, &m.Failed, &m.Pending)
+	if err != nil {
+		return JobMetrics{}, err
+	}
+	return m, nil
+}