Initial commit: notification-elements-demo app

Interactive Angular 19 demo for @sda/notification-elements-ui with
6 sections: Bell & Feed, Notification Center, Inbox, Comments &
Threads, Mention Input, and Full-Featured layout. Includes mock
data, dark mode toggle, and real-time event log.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

node_modules/less/test/browser/runner-browser-spec.js

@@ -0,0 +1,12 @@
+describe('less.js browser behaviour', function() {
+    testLessEqualsInDocument();
+
+    it('has some log messages', function() {
+        expect(logMessages.length).to.be.above(0);
+    });
+
+    for (var i = 0; i < testFiles.length; i++) {
+        var sheet = testSheets[i];
+        testSheet(sheet);
+    }
+});