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/define-lazy-prop/readme.md

@@ -0,0 +1,55 @@
+# define-lazy-prop
+
+> Define a [lazily evaluated](https://en.wikipedia.org/wiki/Lazy_evaluation) property on an object
+
+Useful when the value of a property is expensive to generate, so you want to delay the computation until the property is needed. For example, improving startup performance by deferring nonessential operations.
+
+## Install
+
+```
+$ npm install define-lazy-prop
+```
+
+## Usage
+
+```js
+import defineLazyProperty from 'define-lazy-prop';
+
+const unicorn = {
+	// …
+};
+
+defineLazyProperty(unicorn, 'rainbow', () => expensiveComputation());
+
+app.on('user-action', () => {
+	doSomething(unicorn.rainbow);
+});
+```
+
+## API
+
+### defineLazyProperty(object, propertyName, valueGetter)
+
+#### object
+
+Type: `object`
+
+Object to add the property to.
+
+#### propertyName
+
+Type: `string`
+
+Name of the property to add.
+
+#### valueGetter
+
+Type: `Function`
+
+Called the first time `propertyName` is accessed. Expected to return a value.
+
+## Related
+
+- [lazy-value](https://github.com/sindresorhus/lazy-value) - Create a lazily evaluated value
+- [import-lazy](https://github.com/sindresorhus/import-lazy) - Import a module lazily
+- [p-lazy](https://github.com/sindresorhus/p-lazy) - Create a lazy promise