Phase A.2 - Add expandable Request/Response Headers view

lib/har-parser.js

@@ -53,6 +53,10 @@ function parseHAR(lighthouseResult) {
       isThirdParty: checkIfThirdParty(request.url, lighthouseResult.finalUrl),
       renderBlocking: request.renderBlocking === 'blocking',
       
+      // HTTP Headers
+      requestHeaders: request.requestHeaders || {},
+      responseHeaders: request.responseHeaders || {},
+      
       // Extracted from response headers if available
       cacheControl: request.responseHeaders?.['cache-control'],
       contentEncoding: request.responseHeaders?.['content-encoding']