feature: Prometheus Metrics, Supervisor Dashboard, and Promotion Retry Job

VigilCareRecordsAPI/Models/Records/Events/BatchEventResponse.cs

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+/// <summary>
+/// A single audit trail event for a digitization batch.
+/// Includes the actor's username and full name for display
+/// without requiring a separate user lookup.
+/// </summary>
+public record BatchEventResponse(
+    Guid Id,
+    Guid BatchId,
+    string EventType,
+    Guid ActorUserId,
+    string ActorUsername,
+    string ActorFullName,
+    DateTimeOffset OccurredAt,
+    string? MetadataJson
+);

VigilCareRecordsAPI/Models/Records/Events/CursorPagedResult.cs

@@ -0,0 +1,15 @@
+/// <summary>
+/// Cursor-paginated result set. The cursor is the OccurredAt timestamp
+/// of the last item in this page. Pass it as the "after" query parameter
+/// to get the next page.
+///
+/// This uses the N+1 fetch pattern: fetch pageSize+1 rows, return pageSize,
+/// and use the existence of the extra row to determine HasMore without
+/// a separate COUNT query.
+/// </summary>
+public record CursorPagedResult<T>(
+    IReadOnlyList<T> Items,
+    int PageSize,
+    string? NextCursor,
+    bool HasMore
+);