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/uuid/dist/esm-node/rng.js

@@ -0,0 +1,12 @@
+import crypto from 'crypto';
+const rnds8Pool = new Uint8Array(256); // # of random values to pre-allocate
+
+let poolPtr = rnds8Pool.length;
+export default function rng() {
+  if (poolPtr > rnds8Pool.length - 16) {
+    crypto.randomFillSync(rnds8Pool);
+    poolPtr = 0;
+  }
+
+  return rnds8Pool.slice(poolPtr, poolPtr += 16);
+}