fix(reporting): full-width layout and in-panel vertical scroll

- Reporting page breaks out of max-w-7xl container to use full viewport width
- Table body scrolls within the panel (maxHeight: calc(100vh - 420px)) so you
  no longer need to scroll the entire page to reach the horizontal scrollbar
- Column headers are sticky (position: sticky, top 0) with opaque background
  so they remain visible while scrolling vertically through findings

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/App.js

@@ -965,7 +965,7 @@ export default function App() {
       {/* Scanning line effect */}
       <div className="scan-line"></div>
 
-      <div className="max-w-7xl mx-auto relative z-10">
+      <div className={`${currentPage === 'reporting' ? 'w-full' : 'max-w-7xl mx-auto'} relative z-10`}>
         {/* Header */}
         <div className="mb-8">
           <div className="flex justify-between items-start mb-6">