fix: require auth for chat endpoint

backend-tests/ChatControllerTests.cs

@@ -0,0 +1,17 @@
+using System.Reflection;
+using Microsoft.AspNetCore.Authorization;
+using Nexus.Api.Controllers;
+using Xunit;
+
+namespace Nexus.Api.Tests;
+
+public sealed class ChatControllerTests
+{
+    [Fact]
+    public void ChatController_RequiresAuthorization()
+    {
+        var attribute = typeof(ChatController).GetCustomAttribute<AuthorizeAttribute>();
+
+        Assert.NotNull(attribute);
+    }
+}

backend/Controllers/ChatController.cs

@@ -1,3 +1,4 @@
+using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.RateLimiting;
 using Nexus.Api.DTOs;
@@ -5,6 +6,7 @@ using Nexus.Api.Integrations;
 
 namespace Nexus.Api.Controllers;
 
+[Authorize]
 [ApiController]
 [Route("api/v1/chat")]
 public class ChatController(IAgentRuntime runtime, ILogger<ChatController> logger) : ControllerBase