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/brackets.js

@@ -0,0 +1,51 @@
+function last(array) {
+  return array[array.length - 1]
+}
+
+let brackets = {
+  /**
+   * Parse string to nodes tree
+   */
+  parse(str) {
+    let current = ['']
+    let stack = [current]
+
+    for (let sym of str) {
+      if (sym === '(') {
+        current = ['']
+        last(stack).push(current)
+        stack.push(current)
+        continue
+      }
+
+      if (sym === ')') {
+        stack.pop()
+        current = last(stack)
+        current.push('')
+        continue
+      }
+
+      current[current.length - 1] += sym
+    }
+
+    return stack[0]
+  },
+
+  /**
+   * Generate output string by nodes tree
+   */
+  stringify(ast) {
+    let result = ''
+    for (let i of ast) {
+      if (typeof i === 'object') {
+        result += `(${brackets.stringify(i)})`
+        continue
+      }
+
+      result += i
+    }
+    return result
+  }
+}
+
+module.exports = brackets