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/@tufjs/models/dist/index.d.ts

@@ -0,0 +1,10 @@
+export { MetadataKind } from './base';
+export { ValueError } from './error';
+export { MetaFile, TargetFile } from './file';
+export { Key } from './key';
+export { Metadata } from './metadata';
+export { Root } from './root';
+export { Signature } from './signature';
+export { Snapshot } from './snapshot';
+export { Targets } from './targets';
+export { Timestamp } from './timestamp';