Add connector.js files to expose theme settings in templates

- Create Glimmer component classes for both plugin outlet connectors
- Expose settings object as this.theme getter for template access
- Ensures theme component settings are properly available in Handlebars templates
- Fixes settings access for Discourse 3.5.0 component architecture

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

javascripts/discourse/connectors/above-main-container-outlet/welcome-banner.js

@@ -0,0 +1,7 @@
+import Component from "@glimmer/component";
+
+export default class WelcomeBanner extends Component {
+  get theme() {
+    return settings;
+  }
+}

javascripts/discourse/connectors/below-site-header/welcome-banner-header.js

@@ -0,0 +1,7 @@
+import Component from "@glimmer/component";
+
+export default class WelcomeBannerHeader extends Component {
+  get theme() {
+    return settings;
+  }
+}