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/plugins/postprocess/index.js

@@ -0,0 +1,14 @@
+(function(exports) {
+    var postProcessor = function() {};
+
+    postProcessor.prototype = {
+        process: function (css) {
+            return 'hr {height:50px;}\n' + css;
+        }
+    };
+
+    exports.install = function(less, pluginManager) {
+        pluginManager.addPostProcessor( new postProcessor());
+    };
+
+})(typeof exports === 'undefined' ? this['postProcessorPlugin'] = {} : exports);