Fix Central launch profile: auth middleware, cookie auth, antiforgery, static files

- Add UseAuthentication/UseAuthorization/UseAntiforgery/UseStaticFiles middleware
- Register ASP.NET Core cookie authentication scheme in AddSecurity()
- Update auth endpoints to use SignInAsync/SignOutAsync (proper cookie auth)
- Add [AllowAnonymous] to login page
- Create wwwroot for static file serving
- Regenerate clean EF migration after model changes

Verified with launch profile "ScadaLink Central":
- Host starts, connects to SQL Server, applies EF migrations
- Akka.NET cluster forms (remoting on 8081, node joins self as leader)
- /health/ready returns Healthy (DB + Akka checks)
- LDAP auth works (admin/password via GLAuth → 302 + auth cookie set)
- Login page renders (HTTP 200)
- Unauthenticated requests redirect to /login

src/ScadaLink.Host/Program.cs

@@ -108,6 +108,12 @@ try
             }
         }
 
+        // Middleware pipeline
+        app.UseStaticFiles();
+        app.UseAuthentication();
+        app.UseAuthorization();
+        app.UseAntiforgery();
+
         // WP-12: Map readiness endpoint — returns 503 until all checks pass, 200 when ready
         app.MapHealthChecks("/health/ready", new HealthCheckOptions
         {