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/tar/lib/strip-trailing-slashes.js

@@ -0,0 +1,13 @@
+// warning: extremely hot code path.
+// This has been meticulously optimized for use
+// within npm install on large package trees.
+// Do not edit without careful benchmarking.
+module.exports = str => {
+  let i = str.length - 1
+  let slashesStart = -1
+  while (i > -1 && str.charAt(i) === '/') {
+    slashesStart = i
+    i--
+  }
+  return slashesStart === -1 ? str : str.slice(0, slashesStart)
+}