Add Luna.Core server with SignalR hub, session management, and tool system

Implement the core application server as an ASP.NET web host with:
- SignalR ChatHub for real-time client communication
- Session management with token estimation for context windowing
- Extensible tool system with attribute-based tool discovery
- Chat stream update builder for streaming AI responses
- App configuration with appsettings for development and production

Luna.Core/Tools/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,19 @@
+namespace Luna.Core.Tools.Extensions;
+
+public static class ServiceCollectionExtensions
+{
+    extension(IServiceCollection services)
+    {
+        public IServiceCollection AddTools()
+        {
+            services.AddSingleton<IToolsProvider, ToolsProvider>();
+            
+            typeof(ToolsProvider).Assembly.GetTypes()
+                .Where(t => typeof(IToolbox).IsAssignableFrom(t) && !t.IsInterface && !t.IsAbstract)
+                .ToList()
+                .ForEach(t => services.AddTransient(typeof(IToolbox), t));
+            
+            return services;
+        }
+    }
+}