feat(storage): paginate operations history with prev/next controls

Backend:
- ListStorageJobs(limit, offset) adds OFFSET for pagination
- CountStorageJobs() returns total row count for UI
- handler returns { jobs, total, limit, offset }
- JobManager.List(limit, offset) updated signature

Frontend:
- loadJobs(offset) with default 0
- Pagination UI: 'Mostrando X-Y de Z' + Anterior/Siguiente buttons
- After job start/end, reloads from offset 0
- listStorageJobs(limit, offset) API updated

Tests: fix List/ListStorageJobs calls to include offset=0

internal/storage/jobs_test.go

@@ -54,7 +54,7 @@ func TestJobManagerListEmpty(t *testing.T) {
 	defer d.Close()
 
 	jm := NewJobManager(d, false)
-	jobs, err := jm.List(10)
+	jobs, err := jm.List(10, 0)
 	if err != nil {
 		t.Fatalf("List: %v", err)
 	}
@@ -85,7 +85,7 @@ func TestJobManagerResetOrphans(t *testing.T) {
 		t.Fatalf("ResetOrphans: %v", err)
 	}
 
-	jobs, _ := jm.List(10)
+	jobs, _ := jm.List(10, 0)
 	runningCount := 0
 	queuedCount := 0
 	for _, j := range jobs {