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/Endpoints/Show/GetShowEndpoint.cs

@@ -30,7 +30,8 @@ public class GetShowEndpoint(PyroFetesDbContext pyroFetesDbContext) : Endpoint<I
                 Place = s.Place,
                 Description = s.Description,
                 PyrotechnicImplementationPlan = s.PyrotechnicImplementationPlan,
-                Date = s.Date.HasValue ? s.Date.Value.ToDateTime(TimeOnly.MinValue) : null
+                Date = s.Date.HasValue ? s.Date.Value.ToDateTime(TimeOnly.MinValue) : null,
+                CityId = s.CityId
             })
             .FirstOrDefaultAsync(ct);