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/is-extglob/index.js

@@ -0,0 +1,20 @@
+/*!
+ * is-extglob <https://github.com/jonschlinkert/is-extglob>
+ *
+ * Copyright (c) 2014-2016, Jon Schlinkert.
+ * Licensed under the MIT License.
+ */
+
+module.exports = function isExtglob(str) {
+  if (typeof str !== 'string' || str === '') {
+    return false;
+  }
+
+  var match;
+  while ((match = /(\\).|([@?!+*]\(.*\))/g.exec(str))) {
+    if (match[2]) return true;
+    str = str.slice(match.index + match[0].length);
+  }
+
+  return false;
+};