feat(auditlog): GetExecutionTreeAsync recursive execution-chain query

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

@@ -134,4 +134,45 @@ public interface IAuditLogRepository
         TimeSpan window,
         DateTime? nowUtc = null,
         CancellationToken ct = default);
+
+    /// <summary>
+    /// Audit Log ParentExecutionId feature (Task 8) — given any
+    /// <paramref name="executionId"/> in an execution chain, returns the whole
+    /// chain rooted at the topmost ancestor: one <see cref="ExecutionTreeNode"/>
+    /// per distinct execution, summarising its <c>AuditLog</c> rows. The Central
+    /// UI renders the result as a tree.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The input id may be any node in the chain — a leaf, the root, or a middle
+    /// node. The implementation first walks <em>up</em> via
+    /// <c>ParentExecutionId</c> to find the root, then walks <em>down</em> from
+    /// the root via a recursive CTE, so the full chain is returned regardless of
+    /// entry point.
+    /// </para>
+    /// <para>
+    /// The <c>ParentExecutionId</c> graph is a tree (acyclic by construction —
+    /// each execution is minted fresh and its parent always pre-exists). Both
+    /// the upward walk and the downward CTE are nonetheless bounded at 32 levels
+    /// as a guard against corrupt/pathological data: a depth that exceeds the
+    /// guard raises an error rather than hanging the server. Chains are shallow
+    /// (1-2 levels typical) so the guard is never reached in practice.
+    /// </para>
+    /// <para>
+    /// A "stub" node — an execution that emitted no rows of its own yet is
+    /// referenced by a child via <c>ParentExecutionId</c>, or whose rows have
+    /// been purged — still appears, with <see cref="ExecutionTreeNode.RowCount"/>
+    /// = 0. A purged/missing parent simply ends the upward walk.
+    /// </para>
+    /// <para>
+    /// When no <c>AuditLog</c> row carries <paramref name="executionId"/> in
+    /// either <c>ExecutionId</c> or <c>ParentExecutionId</c>, the result is a
+    /// single stub node for <paramref name="executionId"/> itself
+    /// (<see cref="ExecutionTreeNode.RowCount"/> = 0) — consistent with the
+    /// stub-node treatment of any other row-less execution.
+    /// </para>
+    /// </remarks>
+    Task<IReadOnlyList<ExecutionTreeNode>> GetExecutionTreeAsync(
+        Guid executionId,
+        CancellationToken ct = default);
 }

src/ScadaLink.Commons/Types/Audit/ExecutionTreeNode.cs

@@ -0,0 +1,71 @@
+namespace ScadaLink.Commons.Types.Audit;
+
+/// <summary>
+/// One execution within an execution chain returned by
+/// <see cref="ScadaLink.Commons.Interfaces.Repositories.IAuditLogRepository.GetExecutionTreeAsync"/>.
+/// Each node summarises the <c>AuditLog</c> rows sharing a single
+/// <see cref="ExecutionId"/>; the Central UI renders the set as a tree by
+/// joining <see cref="ParentExecutionId"/> to a parent node's
+/// <see cref="ExecutionId"/>.
+/// </summary>
+/// <remarks>
+/// <para>
+/// <b>Stub nodes.</b> An execution that performed a trust-boundary action but
+/// crossed it without emitting any audit row — or whose own rows have been
+/// purged — still appears as a node when a child references it via
+/// <see cref="ParentExecutionId"/>. Such a stub node has <see cref="RowCount"/>
+/// = 0, empty <see cref="Channels"/>/<see cref="Statuses"/>, null
+/// <see cref="SourceSiteId"/>/<see cref="SourceInstanceId"/>, null timestamps,
+/// and a null <see cref="ParentExecutionId"/> (a purged/ghost parent leaves no
+/// row from which its own parent could be read — the upward walk ends there).
+/// </para>
+/// <para>
+/// <see cref="Channels"/> and <see cref="Statuses"/> are the distinct sets of
+/// the corresponding enum names present across the execution's rows, modelled
+/// as <see cref="IReadOnlyList{T}"/> of string to mirror how the repository's
+/// query filters already pass small bounded sets around.
+/// </para>
+/// </remarks>
+/// <param name="ExecutionId">The execution this node summarises.</param>
+/// <param name="ParentExecutionId">
+/// The <see cref="ExecutionId"/> of the spawning execution, or null for the
+/// root (and for stub nodes, whose own parent is unknowable).
+/// </param>
+/// <param name="RowCount">
+/// Number of <c>AuditLog</c> rows carrying this <see cref="ExecutionId"/>; 0 for
+/// a stub node.
+/// </param>
+/// <param name="Channels">
+/// Distinct <see cref="ScadaLink.Commons.Types.Enums.AuditChannel"/> names
+/// present across this execution's rows; empty for a stub node.
+/// </param>
+/// <param name="Statuses">
+/// Distinct <see cref="ScadaLink.Commons.Types.Enums.AuditStatus"/> names
+/// present across this execution's rows; empty for a stub node.
+/// </param>
+/// <param name="SourceSiteId">
+/// Source site of the execution's rows when consistent; null for a stub node
+/// (or when the rows carry no site).
+/// </param>
+/// <param name="SourceInstanceId">
+/// Source instance of the execution's rows when consistent; null for a stub
+/// node (or when the rows carry no instance).
+/// </param>
+/// <param name="FirstOccurredAtUtc">
+/// Earliest <c>OccurredAtUtc</c> across this execution's rows; null for a stub
+/// node.
+/// </param>
+/// <param name="LastOccurredAtUtc">
+/// Latest <c>OccurredAtUtc</c> across this execution's rows; null for a stub
+/// node.
+/// </param>
+public sealed record ExecutionTreeNode(
+    Guid ExecutionId,
+    Guid? ParentExecutionId,
+    int RowCount,
+    IReadOnlyList<string> Channels,
+    IReadOnlyList<string> Statuses,
+    string? SourceSiteId,
+    string? SourceInstanceId,
+    DateTime? FirstOccurredAtUtc,
+    DateTime? LastOccurredAtUtc);