refactor: replace PostgreSQL placeholders with generic SQL syntax and add audit logging for duplicate entries

- Replace $%d placeholders with ? in logsHandler for database abstraction
- Remove unused argIndex variable in auth.go
- Log duplicate permanent whitelist insertions to audit_log in db.go

db.go

@@ -60,6 +60,10 @@ func AddPermanentEntry(db *sql.DB, entry, apiClientIP string) (bool, error) {
 	_, err := db.Exec(`INSERT INTO perm_whitelist(entry) VALUES(?)`, entry)
 	if err != nil {
 		if isUniqueConstraintError(err) {
+			_, err = db.Exec(`INSERT INTO audit_log(action, cidr, api_client_ip) VALUES('add_perm_duplicate', ?, ?)`, entry, apiClientIP)
+			if err != nil {
+				return false, err
+			}
 			return false, nil
 		}
 		return false, err