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/PyroFetesDbContext.cs

@@ -4,7 +4,7 @@ using ServiceProvider = PyroFetes.Models.ServiceProvider;
 
 namespace PyroFetes;
 
-public class PyroFetesDbContext : DbContext
+public class PyroFetesDbContext(DbContextOptions<PyroFetesDbContext> options) : DbContext(options)
 {
     // Entities
     public DbSet<Availability> Availabilities { get; set; }