Add AuthController with /auth/me user info endpoint

Introduced AuthController secured with [Authorize] attribute.
Provides a GET /auth/me endpoint that returns the authenticated
user's identity details and claims.

Controllers/AuthController.cs

@@ -0,0 +1,24 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+
+namespace FakeNTLMServer.Controllers
+{
+    [ApiController]
+    [Route("[controller]")]
+    [Authorize]
+    public class AuthController : ControllerBase
+    {
+        [HttpGet("me")]
+        public IActionResult GetMe()
+        {
+            var identity = User.Identity;
+            return Ok(new
+            {
+                identity?.Name,
+                identity?.AuthenticationType,
+                identity?.IsAuthenticated,
+                Claims = User.Claims.Select(claim => new { claim.Type, claim.Value })
+            });
+        }
+    }
+}