fix: increase max request body size to prevent 400 Bad Request errors

- Set MaxRequestBodySize to 100MB for large file uploads
- Resolves 'Request Header Or Cookie Too Large' errors
- Applies to Kestrel server in both development and production

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

TaxBaik.Web/Program.cs

@@ -17,6 +17,12 @@ using TaxBaik.Web.Services;
 var builder = WebApplication.CreateBuilder(args);
 var isProduction = builder.Environment.IsProduction();
 
+// HTTP 요청 헤더/쿠키 크기 제한 증가 (400 Bad Request 해결)
+builder.WebHost.ConfigureKestrel(options =>
+{
+    options.Limits.MaxRequestBodySize = 100 * 1024 * 1024; // 100MB
+});
+
 // Serilog 설정
 builder.Host.UseSerilog((context, config) =>
 {