feat(monitoring): aggregate schedule/progress into monitor blobs and expose GET monitor API (#124)

- Add SyncMonitoringAggregationService: drain log-schedule and per-state progress
  queues, merge into per-job JSON under the monitor container (ETag retries)
- Add AggregateSyncMonitoring timer and GET monitor/{area}/{id?}/{schedule?}
- Add monitor response models and live TableVersion rows from SQL
- Add ProcessGlobalChangeTrackingScheduleNextRun (Cronos) for next-run estimates
- Centralize NCRONTAB strings and custom schedule binding in Constants.Schedules
- Report Created progress before queueing sync; set JSON content-type on progress blobs
- Persist sync.TableVersion.Updated and align MERGE/SELECT; fix empty schedule fallback
- Reference Cronos in Directory.Packages.props and csproj

Author: devlead

src/Directory.Packages.props

@@ -19,5 +19,6 @@
     <PackageVersion Include="Microsoft.Azure.Functions.Worker.Sdk" Version="2.0.7" />
     <PackageVersion Include="Microsoft.Data.SqlClient" Version="7.0.0" />
     <PackageVersion Include="NuGetizer" Version="1.4.7" />
+    <PackageVersion Include="Cronos" Version="0.11.1" />
   </ItemGroup>
 </Project>

src/SqlBulkSyncFunction/Constants.cs

@@ -22,6 +22,34 @@ public static class Queues
         /// </summary>
         public const string SyncJobProgressQueue = "syncjobprogress";
     }
+    /// <summary>
+    /// NCRONTAB expressions and configuration keys for <see cref="Functions.ProcessGlobalChangeTrackingSchedule"/> timer triggers.
+    /// </summary>
+    public static class Schedules
+    {
+        /// <summary>
+        /// Configuration / environment key for the <c>Custom</c> schedule (same as the timer binding placeholder without % delimiters).
+        /// </summary>
+        public const string CustomScheduleConfigurationKey = "ProcessGlobalChangeTrackingSchedule";
+
+        /// <summary>
+        /// Timer trigger binding for the custom schedule: <c>%ProcessGlobalChangeTrackingSchedule%</c>.
+        /// </summary>
+        public const string CustomScheduleTimerTrigger = "%" + CustomScheduleConfigurationKey + "%";
+
+        /// <summary>NCRONTAB for <c>Midnight</c> (<c>0 0 0 * * *</c>).</summary>
+        public const string MidnightCron = "0 0 0 * * *";
+
+        /// <summary>NCRONTAB for <c>Noon</c> (<c>0 0 12 * * *</c>).</summary>
+        public const string NoonCron = "0 0 12 * * *";
+
+        /// <summary>NCRONTAB for <c>EveryFiveMinutes</c> (<c>5 */5 * * * *</c>).</summary>
+        public const string EveryFiveMinutesCron = "5 */5 * * * *";
+
+        /// <summary>NCRONTAB for <c>EveryHour</c> (<c>10 0 * * * *</c>).</summary>
+        public const string EveryHourCron = "10 0 * * * *";
+    }
+
     public static class Containers
     {
         /// <summary>
@@ -30,5 +58,19 @@ public static class Containers
         public const string SyncJob = "syncjob";
 
         public const string SyncSchedule = "syncschedule";
+
+        /// <summary>
+        /// Blob container for per-job monitoring aggregates (written by the aggregation timer).
+        /// </summary>
+        public const string Monitor = "monitor";
+    }
+
+    /// <summary>
+    /// Content types for Azure Blob uploads.
+    /// </summary>
+    public static class BlobContentTypes
+    {
+        /// <summary>JSON documents (UTF-8).</summary>
+        public const string Json = "application/json; charset=utf-8";
     }
 }

src/SqlBulkSyncFunction/Functions/AggregateSyncMonitoring.cs

@@ -0,0 +1,24 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Azure.Functions.Worker;
+using SqlBulkSyncFunction.Services;
+
+namespace SqlBulkSyncFunction.Functions;
+
+/// <summary>
+/// Timer that drains schedule and progress queues in order and refreshes per-job aggregate blobs under the monitor container.
+/// </summary>
+public sealed class AggregateSyncMonitoring(SyncMonitoringAggregationService aggregationService)
+{
+    /// <summary>
+    /// Runs every minute on the minute (UTC).
+    /// </summary>
+    [Function(nameof(AggregateSyncMonitoring))]
+    public Task Run(
+#pragma warning disable IDE0060 // Remove unused parameter
+        [TimerTrigger("0 */1 * * * *")] TimerInfo timerInfo,
+#pragma warning restore IDE0060 // Remove unused parameter
+        CancellationToken cancellationToken
+    )
+        => aggregationService.ProcessAllQueuesAsync(cancellationToken);
+}