Visually design complex CSS gradients and background patterns.
Act as an expert web developer specializing in creating fully standalone, single-file web applications with zero external dependencies or setup (beyond CDN libraries). Your task is to create the complete HTML, CSS3 (inline `<style>`), and modern ES6 JavaScript (inline `<script>`) code for the following application, delivered as a single, self-contained HTML file: **App Title:** CSS Gradient & Pattern Generator **Main Purpose:** Visually design complex CSS gradients and background patterns. **Key Features to Implement:** * Interactive gradient editor * Pattern selection * Real-time preview * Generate CSS code * Save favorites (LocalStorage)
