Fix relay trigger validation to use correct variable references

Remove redundant checkbox selectors that used wrong class names (.high-alarm-checkbox
instead of .high-alarm-enabled). The validation now correctly uses the already-defined
highAlarmEnabled and lowAlarmEnabled variables.

Co-authored-by: dorkmo <[email protected]>

Author: Copilot

TankAlarm-112025-Server-BluesOpta/TankAlarm-112025-Server-BluesOpta.ino

@@ -1042,8 +1042,6 @@ static const char CONFIG_GENERATOR_HTML[] PROGMEM = R"HTML(
               alert("You have set a relay target but have not selected any relay outputs for " + name + ". The configuration will be incomplete.");
             }
             // Validation: warn if relay trigger is set to an alarm type that is not enabled
-            const highAlarmEnabled = card.querySelector('.high-alarm-checkbox')?.checked;
-            const lowAlarmEnabled = card.querySelector('.low-alarm-checkbox')?.checked;
             if ((relayTrigger === 'high' && !highAlarmEnabled) ||
                 (relayTrigger === 'low' && !lowAlarmEnabled)) {
               alert(`Warning: Relay for ${name} is set to trigger on "${relayTrigger}" alarm, but that alarm type is not enabled.`);