Add Content Breakdown & Domain Analysis

Features Added:
- Canvas-based pie chart showing resource distribution by type
- Content breakdown statistics table
- Compression savings percentage display
- Resource counts and sizes by type
- Automatic rendering after test completion

Technical implementation - Created breakdown.js with drawPieChart and renderContentBreakdown functions

main.js

@@ -117,6 +117,11 @@ function displayResults(data) {
             window.open(`/waterfall.html?id=${data.id}`, '_blank');
         };
     }
+    
+    // Load content breakdown
+    if (typeof renderContentBreakdown === 'function') {
+        renderContentBreakdown(data.id);
+    }
 
     resultsArea.classList.add('visible');