Refactor plugin with improved architecture and new features

- Eliminated code duplication by creating common HTTP request function
- Added configurable SSL verification setting for development/production
- Implemented smart caching system with 1-hour cache duration
- Enhanced admin interface with cache management and better styling
- Improved error handling and user experience
- Added comprehensive documentation and troubleshooting guide
- Updated README with new features and configuration options

css/fw-store-embed.css

@@ -39,4 +39,34 @@
 .tile__heading {
     font-size: 0.88em;  /* Reduced font size for product titles */
     font-weight: bold;
+}
+
+/* Admin page styles */
+.shortcode-info {
+    background: #fff;
+    border: 1px solid #ccd0d4;
+    border-radius: 4px;
+    padding: 20px;
+    margin-top: 20px;
+}
+
+.shortcode-info h3 {
+    margin-top: 0;
+    color: #23282d;
+}
+
+.shortcode-info code {
+    background: #f1f1f1;
+    padding: 2px 6px;
+    border-radius: 3px;
+    font-family: 'Courier New', monospace;
+}
+
+.shortcode-info p {
+    margin: 10px 0;
+}
+
+.shortcode-info em {
+    color: #666;
+    font-style: italic;
 }