feat: fence scheduler next-due updates (AEG-V15-036)

Adds dispatch revision CAS to dispatched, skip, and release schedule mutations. Targeted Release evidence: 8/8 passed. PostgreSQL concurrency rehearsal remains required; WBS stays IN_PROGRESS.

src/KArtSell.Modules.ModelOperations/Application/ModelOperationsContracts.cs

@@ -17,6 +17,7 @@ public sealed record DueModelOperation(
     string Queue,
     string IdempotencyKey,
     int ScheduleVersion,
+    int DispatchRevision,
     DateTimeOffset ScheduledFor,
     string CatchUpPolicy,
     int MaxCatchUp);
@@ -52,6 +53,7 @@ public interface IModelScheduleRepository
     Task MarkDispatchedAsync(
         Guid scheduleId,
         string leaseOwner,
+        int expectedDispatchRevision,
         string backgroundJobId,
         DateTimeOffset dispatchedAt,
         DateTimeOffset nextDueAt,
@@ -60,6 +62,7 @@ public interface IModelScheduleRepository
     Task AdvanceWithoutDispatchAsync(
         Guid scheduleId,
         string leaseOwner,
+        int expectedDispatchRevision,
         DateTimeOffset advancedAt,
         DateTimeOffset nextDueAt,
         CancellationToken cancellationToken);
@@ -67,6 +70,7 @@ public interface IModelScheduleRepository
     Task ReleaseAsync(
         Guid scheduleId,
         string leaseOwner,
+        int expectedDispatchRevision,
         string reasonCode,
         DateTimeOffset releasedAt,
         CancellationToken cancellationToken);