feat(ui): AuditResultsGrid + AuditLogQueryService with keyset paging (#23 M7)

Adds the results grid + query facade for the central Audit Log page
(#23 M7-T3):

* IAuditLogQueryService / AuditLogQueryService — CentralUI facade over
  IAuditLogRepository.QueryAsync so the grid can be tested with a stubbed
  query source. Default page size is 100; callers can override per call.

* AuditResultsGrid.razor + .razor.cs — Blazor Server component (Bootstrap
  only, no third-party UI libs). Renders the 10 columns from
  Component-AuditLog.md §10 (OccurredAtUtc, Site, Channel, Kind, Status,
  Target, Actor, DurationMs, HttpStatus, ErrorMessage). Keyset-paged via
  the last visible row's (OccurredAtUtc, EventId) as the cursor; Next-page
  button disabled when the current page is short (no count query). Row
  clicks emit OnRowSelected(AuditEvent) for Bundle C's drilldown drawer.
  Status badges are colour-coded (Delivered=green; Failed/Parked/Discarded
  =red; other=gray). Error messages truncated to 80 chars with full text
  on hover.

* Column model framework: a ColumnOrder [Parameter] reorders columns by
  stable string keys; unknown keys are dropped. M7 scope decision (in the
  class doc): the framework is in place but drag-reorder / resize UX is
  not implemented — M7.x can add persisted-per-user reordering without
  rewriting the column model.

* AuditLogPage wired: hosts AuditFilterBar + AuditResultsGrid, threads
  the filter through and stubs OnRowSelected for Bundle C.

* AuditLogQueryService registered as scoped in AddCentralUI.

* Tests: 4 grid bUnit tests (10 columns rendered, next-page cursor
  carries last row, row click raises callback, badge classes for
  Failed vs Delivered), 2 service tests (filter+paging pass-through,
  default page size of 100). AuditLogPageScaffoldTests updated to
  provide the new ISiteRepository + IAuditLogQueryService stubs the
  page now resolves.

src/ScadaLink.CentralUI/ServiceCollectionExtensions.cs

@@ -3,6 +3,7 @@ using Microsoft.Extensions.DependencyInjection;
 using ScadaLink.CentralUI.Auth;
 using ScadaLink.CentralUI.Components.Shared;
 using ScadaLink.CentralUI.ScriptAnalysis;
+using ScadaLink.CentralUI.Services;
 
 namespace ScadaLink.CentralUI;
 
@@ -27,6 +28,10 @@ public static class ServiceCollectionExtensions
         // Components/Shared/IDialogService.cs.
         services.AddScoped<IDialogService, DialogService>();
 
+        // Audit Log (#23 M7-T3): CentralUI facade over IAuditLogRepository so the
+        // results grid can be tested with a stubbed query source.
+        services.AddScoped<IAuditLogQueryService, AuditLogQueryService>();
+
         // Roslyn-backed C# analysis for the Monaco script editor.
         // Scoped because SharedScriptCatalog wraps a scoped service.
         services.AddMemoryCache(o => o.SizeLimit = 200);