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.

tests/ScadaLink.CentralUI.Tests/Pages/AuditLogPagePermissionTests.cs

@@ -46,6 +46,15 @@ namespace ScadaLink.CentralUI.Tests.Pages;
 /// </summary>
 public class AuditLogPagePermissionTests : BunitContext
 {
+    public AuditLogPagePermissionTests()
+    {
+        // The page hosts AuditResultsGrid, whose OnAfterRenderAsync wires the
+        // column resize/reorder UX via audit-grid.js (a sessionStorage load +
+        // an init call). Loose mode lets those unconfigured JS calls no-op so
+        // the permission-gating tests need not configure browser interop.
+        JSInterop.Mode = JSRuntimeMode.Loose;
+    }
+
     private static ClaimsPrincipal BuildPrincipal(params string[] roles)
     {
         var claims = new List<Claim> { new("Username", "tester") };