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/zone.js/lib/zone.d.ts

@@ -0,0 +1,41 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.dev/license
+ */
+import { EventTask as _EventTask, HasTaskState as _HasTaskState, MacroTask as _MacroTask, MicroTask as _MicroTask, PatchFn, Task as _Task, TaskData as _TaskData, TaskState as _TaskState, TaskType as _TaskType, UncaughtPromiseError as _UncaughtPromiseError, Zone as _Zone, ZoneDelegate as _ZoneDelegate, ZoneFrame, ZonePrivate, ZoneSpec as _ZoneSpec, ZoneType as _ZoneType } from './zone-impl';
+declare global {
+    const Zone: ZoneType;
+    type Zone = _Zone;
+    type ZoneType = _ZoneType;
+    type _PatchFn = PatchFn;
+    type _ZonePrivate = ZonePrivate;
+    type _ZoneFrame = ZoneFrame;
+    type UncaughtPromiseError = _UncaughtPromiseError;
+    type ZoneSpec = _ZoneSpec;
+    type ZoneDelegate = _ZoneDelegate;
+    type HasTaskState = _HasTaskState;
+    type TaskType = _TaskType;
+    type TaskState = _TaskState;
+    type TaskData = _TaskData;
+    type Task = _Task;
+    type MicroTask = _MicroTask;
+    type MacroTask = _MacroTask;
+    type EventTask = _EventTask;
+    /**
+     * Extend the Error with additional fields for rewritten stack frames
+     */
+    interface Error {
+        /**
+         * Stack trace where extra frames have been removed and zone names added.
+         */
+        zoneAwareStack?: string;
+        /**
+         * Original stack trace with no modifications
+         */
+        originalStack?: string;
+    }
+}
+export declare function loadZone(): ZoneType;