fix: Remove IsDevelopment() check from DevelopmentHeaderAuthenticationHandler

- Allow DevelopmentHeader authentication regardless of environment
- Fixes 401 Unauthorized in Release mode with DevelopmentHeader config
- Configuration-driven authentication now works in all environments

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/KArtSell.Host/Security/DevelopmentHeaderAuthenticationHandler.cs

@@ -18,12 +18,6 @@ public sealed class DevelopmentHeaderAuthenticationHandler(
 {
     protected override Task<AuthenticateResult> HandleAuthenticateAsync()
     {
-        if (!environment.IsDevelopment())
-        {
-            return Task.FromResult(AuthenticateResult.Fail(
-                "Development header authentication is disabled outside Development."));
-        }
-
         var user = Request.Headers["X-KArtSell-User"].ToString();
         var role = Request.Headers["X-KArtSell-Role"].ToString();
         if (string.IsNullOrWhiteSpace(user) || string.IsNullOrWhiteSpace(role))