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/json5/lib/register.js

@@ -0,0 +1,13 @@
+const fs = require('fs')
+const JSON5 = require('./')
+
+// eslint-disable-next-line node/no-deprecated-api
+require.extensions['.json5'] = function (module, filename) {
+    const content = fs.readFileSync(filename, 'utf8')
+    try {
+        module.exports = JSON5.parse(content)
+    } catch (err) {
+        err.message = filename + ': ' + err.message
+        throw err
+    }
+}