feat(centralui): column resize and reorder for the audit results grid

Adds drag-to-resize and drag-to-reorder column UX to AuditResultsGrid,
with chosen widths + column order persisted in browser sessionStorage.

- wwwroot/js/audit-grid.js: dependency-free helper — pointer-driven
  resize handles, native HTML5 drag-and-drop reorder, and a
  sessionStorage save/load wrapper (mirrors treeview-storage.js).
- AuditResultsGrid: renders a resize handle per <th>, makes headers
  draggable, applies persisted widths via a --audit-col-width custom
  property, and wires reorder into the existing ColumnOrder /
  OrderedColumns() mechanism. JS-invokable OnColumnResized /
  OnColumnReordered persist + re-render. A stored order naming an
  unknown column degrades gracefully (drops unknown keys, appends
  missing columns in default order); widths clamp to a 64px minimum.
- AuditResultsGrid.razor.css: subtle scoped styling for the resize
  handle affordance and the reorder drop-target highlight.
- App.razor references audit-grid.js alongside the other scripts.
- Tests: 6 new bUnit tests for the load/apply/persist logic and
  graceful degradation; a new AuditGridColumnTests Playwright suite
  for the drag UX + reload persistence. Audit page bUnit tests set
  loose JSInterop mode since the grid now calls into audit-grid.js.

src/ScadaLink.Host/Components/App.razor

@@ -77,6 +77,7 @@
     </script>
     <script src="/js/treeview-storage.js"></script>
     <script src="_content/ScadaLink.CentralUI/js/monaco-init.js"></script>
+    <script src="_content/ScadaLink.CentralUI/js/audit-grid.js"></script>
     <script src="/lib/bootstrap/js/bootstrap.bundle.min.js"></script>
 </body>
 </html>