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/ws/lib/constants.js

@@ -0,0 +1,19 @@
+'use strict';
+
+const BINARY_TYPES = ['nodebuffer', 'arraybuffer', 'fragments'];
+const hasBlob = typeof Blob !== 'undefined';
+
+if (hasBlob) BINARY_TYPES.push('blob');
+
+module.exports = {
+  BINARY_TYPES,
+  CLOSE_TIMEOUT: 30000,
+  EMPTY_BUFFER: Buffer.alloc(0),
+  GUID: '258EAFA5-E914-47DA-95CA-C5AB0DC85B11',
+  hasBlob,
+  kForOnEventAttribute: Symbol('kIsForOnEventAttribute'),
+  kListener: Symbol('kListener'),
+  kStatusCode: Symbol('status-code'),
+  kWebSocket: Symbol('websocket'),
+  NOOP: () => {}
+};