fix: Card success styling and ensure list support

Fixed two email rendering issues:

1. Card Success Styling
   - Was using hero gradient (purple) instead of green theme
   - Now uses proper green background (#f0fdf4) with green border
   - Info card: blue theme with border
   - Warning card: orange theme with border
   - Hero card: keeps gradient as intended

2. List Support Verification
   - MarkdownParser already supports bullet lists
   - Supports: *, -, •, ✓, ✔ as list markers
   - Properly converts to <ul><li> HTML
   - Works in both visual editor and email preview

Card Types Now:
- default: white background
- hero: gradient background (purple)
- success: green background with left border
- info: blue background with left border
- warning: orange background with left border

includes/Core/Notifications/EmailRenderer.php

@@ -349,8 +349,8 @@ class EmailRenderer {
 		if ($type !== 'default') {
 			$class .= ' card-' . esc_attr($type);
 			
-			// Apply gradient and text color for hero/success cards
-			if ($type === 'hero' || $type === 'success') {
+			// Apply gradient and text color for hero cards
+			if ($type === 'hero') {
 				$style .= sprintf(
 					' background: linear-gradient(135deg, %s 0%%, %s 100%%);',
 					esc_attr($hero_gradient_start),
@@ -365,6 +365,18 @@ class EmailRenderer {
 					$content
 				);
 			}
+			// Success card - green theme
+			elseif ($type === 'success') {
+				$style .= ' background-color: #f0fdf4; border-left: 4px solid #22c55e;';
+			}
+			// Info card - blue theme
+			elseif ($type === 'info') {
+				$style .= ' background-color: #f0f7ff; border-left: 4px solid #0071e3;';
+			}
+			// Warning card - orange theme
+			elseif ($type === 'warning') {
+				$style .= ' background-color: #fff8e1; border-left: 4px solid #ff9800;';
+			}
 		}
 		
 		// Add background image