Fix FastEndpoints/Swagger wiring and missing required fields in DTOs

- Register FastEndpoints, SwaggerDocument, DbContext in Program.cs
- Add DbContextOptions constructor to PyroFetesDbContext
- Add CityId to Show DTOs and endpoints (NOT NULL in DB)
- Add F4T2NumberApproval/F4T2ExpirationDate to Staff DTOs and endpoints
- Simplify DeleteShow to rely on DB cascade instead of manual includes
- Default NOT NULL string fields to empty string on create

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

PyroFetes/Program.cs

@@ -1,19 +1,25 @@
+using FastEndpoints;
+using FastEndpoints.Swagger;
+using Microsoft.EntityFrameworkCore;
+using PyroFetes;
+
 var builder = WebApplication.CreateBuilder(args);
 
-// Add services to the container.
-// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
-builder.Services.AddEndpointsApiExplorer();
-builder.Services.AddSwaggerGen();
+builder.Services.AddDbContext<PyroFetesDbContext>(options =>
+    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));
+
+builder.Services.AddFastEndpoints();
+builder.Services.SwaggerDocument();
 
 var app = builder.Build();
 
-// Configure the HTTP request pipeline.
 if (app.Environment.IsDevelopment())
 {
-    app.UseSwagger();
-    app.UseSwaggerUI();
+    app.UseSwaggerGen();
 }
 
 app.UseHttpsRedirection();
+app.UseFastEndpoints();
 
-app.Run();
+app.Run();
+