fix(migration): add index for traffic log on timestamp, user_id, and subscribe_id

initialize/migrate/database/02110_traffic_log_index.down.sql

@@ -0,0 +1 @@
+DROP INDEX idx_traffic_log_time_user_sub ON traffic_log;

initialize/migrate/database/02110_traffic_log_index.up.sql

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+CREATE INDEX idx_traffic_log_time_user_sub ON traffic_log (timestamp, user_id, subscribe_id);