feat(commons): add IAuditWriter and ICentralAuditWriter (#23)

src/ScadaLink.Commons/Interfaces/Services/IAuditWriter.cs

@@ -0,0 +1,17 @@
+using ScadaLink.Commons.Entities.Audit;
+
+namespace ScadaLink.Commons.Interfaces.Services;
+
+/// <summary>
+/// Boundary-side abstraction for emitting Audit Log (#23) events.
+/// Implementations on the site write to local SQLite hot-path; on central they write to MS SQL directly.
+/// Failures must NEVER abort the user-facing action.
+/// </summary>
+public interface IAuditWriter
+{
+    /// <summary>
+    /// Persist an audit event. Best-effort: implementations must swallow/log internal failures
+    /// rather than propagating them to the calling boundary code.
+    /// </summary>
+    Task WriteAsync(AuditEvent evt, CancellationToken ct = default);
+}

src/ScadaLink.Commons/Interfaces/Services/ICentralAuditWriter.cs

@@ -0,0 +1,16 @@
+using ScadaLink.Commons.Entities.Audit;
+
+namespace ScadaLink.Commons.Interfaces.Services;
+
+/// <summary>
+/// Central-only audit writer for the direct-write path (Notification Outbox dispatch, Inbound API).
+/// Distinct from <see cref="IAuditWriter"/> so DI binding can differ between site and central hosts.
+/// </summary>
+public interface ICentralAuditWriter
+{
+    /// <summary>
+    /// Persist an audit event into the central AuditLog table directly (bypassing site telemetry).
+    /// Best-effort: implementations must swallow/log internal failures rather than propagating them.
+    /// </summary>
+    Task WriteAsync(AuditEvent evt, CancellationToken ct = default);
+}