Implement InMemory Transport Layer for StellaOps Router

- Added InMemoryTransportOptions class for configuration settings including timeouts and latency.
- Developed InMemoryTransportServer class to handle connections, frame processing, and event management.
- Created ServiceCollectionExtensions for easy registration of InMemory transport services.
- Established project structure and dependencies for InMemory transport library.
- Implemented comprehensive unit tests for endpoint discovery, connection management, request/response flow, and streaming capabilities.
- Ensured proper handling of cancellation, heartbeat, and hello frames within the transport layer.

src/Policy/StellaOps.Policy.Engine/Program.cs

@@ -290,4 +290,9 @@ app.MapOverrides();
 app.MapProfileExport();
 app.MapProfileEvents();
 
+// Phase 5: Multi-tenant PostgreSQL-backed API endpoints
+app.MapPolicySnapshotsApi();
+app.MapViolationEventsApi();
+app.MapConflictsApi();
+
 app.Run();