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/semver/ranges/valid.js

@@ -0,0 +1,11 @@
+const Range = require('../classes/range')
+const validRange = (range, options) => {
+  try {
+    // Return '*' instead of '' so that truthiness works.
+    // This will throw if it's invalid anyway
+    return new Range(range, options).range || '*'
+  } catch (er) {
+    return null
+  }
+}
+module.exports = validRange