FIX: Use native checkbox to properly update model on change

The PreferenceCheckbox component doesn't properly propagate checkbox
state changes back to the model when used in plugin outlet contexts.
This caused the subscription preference to not be saved when users
toggled the checkbox.

Replace PreferenceCheckbox with a native checkbox element and an
explicit @action handler that calls model.set() when the checkbox
changes. This ensures the model value is properly updated before
the preferences are saved to the server.

Author: ZogStriP

assets/javascripts/discourse/connectors/user-preferences-emails/subscribe-newsletter-section.gjs

@@ -1,6 +1,7 @@
 import Component from "@glimmer/component";
+import { on } from "@ember/modifier";
+import { action } from "@ember/object";
 import { service } from "@ember/service";
-import PreferenceCheckbox from "discourse/components/preference-checkbox";
 import { i18n } from "discourse-i18n";
 
 export default class SubscribeNewsletterSection extends Component {
@@ -10,17 +11,32 @@ export default class SubscribeNewsletterSection extends Component {
     return this.site.newsletter_integration_plugin_configured;
   }
 
+  @action
+  updateSubscription(event) {
+    this.args.outletArgs.model.set(
+      "newsletter_integration_subscribe_global_newsletter",
+      event.target.checked
+    );
+  }
+
   <template>
     {{#if this.showSubscribeSection}}
       <div class="control-group newsletter-integration-subscribe-section">
         <label class="control-label">{{i18n
             "discourse_newsletter_integration.preferences.section_head"
           }}</label>
-        <PreferenceCheckbox
-          @labelKey="discourse_newsletter_integration.preferences.checkbox_description"
-          @checked={{@outletArgs.model.newsletter_integration_subscribe_global_newsletter}}
-          class="subscribe-checkbox"
-        />
+        <div class="controls subscribe-checkbox">
+          <label class="checkbox-label">
+            <input
+              type="checkbox"
+              checked={{@outletArgs.model.newsletter_integration_subscribe_global_newsletter}}
+              {{on "change" this.updateSubscription}}
+            />
+            {{i18n
+              "discourse_newsletter_integration.preferences.checkbox_description"
+            }}
+          </label>
+        </div>
       </div>
     {{/if}}
   </template>