Merge pull request #969 from adamantike/fix/implement-total-filesize-stat

fix: Add implementation for total filesize statistic

backend/handler/database/stats_handler.py

@@ -42,4 +42,5 @@ class DBStatsHandler(DBBaseHandler):
 
     @begin_session
     def get_total_filesize(self, session: Session = None) -> int:
-        return 0
+        """Get the total filesize of all roms in the database, in bytes."""
+        return session.scalar(select(func.sum(Rom.file_size_bytes)).select_from(Rom))