Implement MongoDB-based storage for Pack Run approval, artifact, log, and state management

- Added MongoPackRunApprovalStore for managing approval states with MongoDB.
- Introduced MongoPackRunArtifactUploader for uploading and storing artifacts.
- Created MongoPackRunLogStore to handle logging of pack run events.
- Developed MongoPackRunStateStore for persisting and retrieving pack run states.
- Implemented unit tests for MongoDB stores to ensure correct functionality.
- Added MongoTaskRunnerTestContext for setting up MongoDB test environment.
- Enhanced PackRunStateFactory to correctly initialize state with gate reasons.

src/Cli/__Tests/StellaOps.Cli.Tests/Services/BackendOperationsClientTests.cs

@@ -574,7 +574,7 @@ public sealed class BackendOperationsClientTests
         var result = await client.TriggerJobAsync("test", new Dictionary<string, object?>(), CancellationToken.None);
 
         Assert.True(result.Success);
-        var metadata = Assert.NotNull(tokenClient.LastAdditionalParameters);
+        var metadata = Assert.IsAssignableFrom<IReadOnlyDictionary<string, string>>(tokenClient.LastAdditionalParameters);
         Assert.Equal("Resume operations", metadata["operator_reason"]);
         Assert.Equal("INC-6006", metadata["operator_ticket"]);
         Assert.Equal("Historical rebuild", metadata["backfill_reason"]);