Replace concat() with plus due to sqlite3 limitation

app/queries/monthly_stats.py

@@ -29,7 +29,7 @@ def get_all_monthly_analytics(end_date:str = 'now'):
                 group by counter_id, strftime('%m', timestamp),  strftime('%Y', timestamp)
             )
             select 
-                concat(m.m,', ',m.y) as "month",
+                m.m + ', ' + m.y as "month",
                 case 
                     when counter_id is null then json_object()
                     else json_group_object(name, count)