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/db/queries_storage_test.go

@@ -14,7 +14,7 @@ func TestListStorageJobsEmptyReturnsSlice(t *testing.T) {
 		t.Fatalf("migrate: %v", err)
 	}
 
-	jobs, err := d.ListStorageJobs(50)
+	jobs, err := d.ListStorageJobs(50, 0)
 	if err != nil {
 		t.Fatalf("ListStorageJobs: %v", err)
 	}