feat(ui): add Node column + filter to AuditLog grid

src/ScadaLink.Commons/Interfaces/Repositories/IAuditLogRepository.cs

@@ -175,4 +175,12 @@ public interface IAuditLogRepository
     Task<IReadOnlyList<ExecutionTreeNode>> GetExecutionTreeAsync(
         Guid executionId,
         CancellationToken ct = default);
+
+    /// <summary>
+    /// Returns the distinct, non-null <c>SourceNode</c> values present in the
+    /// <c>AuditLog</c> table, in ascending order. Backs the Audit Log page's
+    /// "Node" multi-select filter dropdown — the Central UI caches the result
+    /// for ~60s so the repository is hit at most once per minute per circuit.
+    /// </summary>
+    Task<IReadOnlyList<string>> GetDistinctSourceNodesAsync(CancellationToken ct = default);
 }