Refactor: Use session-based TempData provider

Switch from cookie-based to session-based TempData to avoid
cookie size limits when storing AI categorization proposals.
Chain AddSessionStateTempDataProvider() to AddRazorPages().

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

MoneyMap/Program.cs

@@ -10,7 +10,6 @@ CultureInfo.DefaultThreadCurrentUICulture = culture;
 
 var builder = WebApplication.CreateBuilder(args);
 
-builder.Services.AddRazorPages();
 builder.Services.AddDbContext<MoneyMapContext>(options =>
     options.UseSqlServer(builder.Configuration.GetConnectionString("MoneyMapDb")));
 
@@ -27,6 +26,10 @@ builder.Services.AddSession(options =>
     options.IOTimeout = TimeSpan.FromMinutes(5); // Increase timeout for large data
 });
 
+// Use session-based TempData provider to avoid cookie size limits
+builder.Services.AddRazorPages()
+    .AddSessionStateTempDataProvider();
+
 // Core transaction and import services
 builder.Services.AddScoped<ITransactionImporter, TransactionImporter>();
 builder.Services.AddScoped<ICardResolver, CardResolver>();