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/escalade/index.d.ts

@@ -0,0 +1,15 @@
+type Promisable<T> = T | Promise<T>;
+
+declare namespace escalade {
+	export type Callback = (
+		directory: string,
+		files: string[],
+	) => Promisable<string | false | void>;
+}
+
+declare function escalade(
+	directory: string,
+	callback: escalade.Callback,
+): Promise<string | void>;
+
+export = escalade;