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/autoprefixer/lib/hacks/flex-wrap.js

@@ -0,0 +1,19 @@
+let flexSpec = require('./flex-spec')
+let Declaration = require('../declaration')
+
+class FlexWrap extends Declaration {
+  /**
+   * Don't add prefix for 2009 spec
+   */
+  set(decl, prefix) {
+    let spec = flexSpec(prefix)[0]
+    if (spec !== 2009) {
+      return super.set(decl, prefix)
+    }
+    return undefined
+  }
+}
+
+FlexWrap.names = ['flex-wrap']
+
+module.exports = FlexWrap