Changed checked value to use portal plans on toggle (#18708)

no issue

- this adds a bit more logic to ensure the portal plans remain consistent with the tier's visibility in the portal preview.
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### <samp>🤖 Generated by Copilot at 74fd5c4</samp>

Refactored the `Free` tier checkbox in the portal signup options
component to use the `portalPlans` array. This improves the consistency
and reliability of the portal plans settings.

apps/admin-x-settings/src/components/settings/membership/portal/SignupOptions.tsx

@@ -66,13 +66,22 @@ const SignupOptions: React.FC<{
         localTiers.forEach((tier) => {
             if (tier.name === 'Free') {
                 tiersCheckboxes.push({
-                    checked: tier.visibility === 'public',
+                    checked: (portalPlans.includes('free')),
                     disabled: isDisabled,
                     label: 'Free',
                     value: 'free',
                     onChange: (checked) => {
+                        if (portalPlans.includes('free') && !checked) {
+                            portalPlans.splice(portalPlans.indexOf('free'), 1);
+                        }
+
+                        if (!portalPlans.includes('free') && checked) {
+                            portalPlans.push('free');
+                        }
+
+                        updateSetting('portal_plans', JSON.stringify(portalPlans));
+
                         updateTier({...tier, visibility: checked ? 'public' : 'none'});
-                        togglePlan('free');
                     }
                 });
             }