security: remediate vulnerabilities and issues from codebase audit

backend/database/database.go

@@ -182,3 +182,9 @@ func (db *DB) AddAuditLog(action, details, ip string) error {
 	_, err := db.Exec("INSERT INTO audit_log (action, details, ip_address) VALUES (?, ?, ?)", action, details, ip)
 	return err
 }
+
+// CleanOldAuditLogs deletes audit logs older than 30 days.
+func (db *DB) CleanOldAuditLogs() error {
+	_, err := db.Exec("DELETE FROM audit_log WHERE timestamp < datetime('now', '-30 days')")
+	return err
+}