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/components/pages/ReportingPage.js

@@ -801,7 +801,7 @@ export default function ReportingPage() {
                         <p style={{ fontFamily: 'monospace', fontSize: '0.75rem', color: '#475569' }}>Click Sync to load findings data</p>
                     </div>
                 ) : (
-                    <div style={{ overflowX: 'auto', marginTop: '0.75rem' }}>
+                    <div style={{ overflowX: 'auto', overflowY: 'auto', maxHeight: 'calc(100vh - 420px)', minHeight: '200px', marginTop: '0.75rem' }}>
                         <table style={{ width: '100%', borderCollapse: 'collapse', fontSize: '0.75rem', fontFamily: 'sans-serif' }}>
                             <thead>
                                 <tr style={{ borderBottom: '1px solid rgba(14,165,233,0.2)' }}>
@@ -821,8 +821,9 @@ export default function ReportingPage() {
                                                     whiteSpace: 'nowrap',
                                                     cursor: def?.sortable ? 'pointer' : 'default',
                                                     userSelect: 'none',
-                                                    background: 'rgba(15,26,46,0.6)',
-                                                    position: 'relative',
+                                                    background: 'rgb(10, 20, 36)',
+                                                    position: 'sticky', top: 0, zIndex: 10,
+                                                    boxShadow: '0 1px 0 rgba(14,165,233,0.2)',
                                                 }}
                                             >
                                                 <span style={{ display: 'inline-flex', alignItems: 'center' }}>