Add rollback ratio alert tuning parameters

Introduced new parameters to fine-tune rollback ratio alerts and reduce false positives on low-traffic databases. Adjusted evaluation logic to account for minimum rollback counts and transaction volumes, ensuring more reliable alert thresholds. Updated .env.example and descriptions for better configuration clarity.

.env.example

@@ -45,6 +45,10 @@ POLL_INTERVAL_SECONDS=30
 # Active Connection Ratio alert is only evaluated when total sessions
 # are at least this number (reduces false positives on low-traffic DBs).
 ALERT_ACTIVE_CONNECTION_RATIO_MIN_TOTAL_CONNECTIONS=5
+# Rollback Ratio tuning to reduce false positives on low traffic.
+ALERT_ROLLBACK_RATIO_WINDOW_MINUTES=15
+ALERT_ROLLBACK_RATIO_MIN_TOTAL_TRANSACTIONS=100
+ALERT_ROLLBACK_RATIO_MIN_ROLLBACKS=10
 # Initial admin bootstrap user (created on first startup if not present).
 INIT_ADMIN_EMAIL=admin@example.com
 INIT_ADMIN_PASSWORD=ChangeMe123!