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/DTO/Show/Request/CreateShowDto.cs

@@ -7,4 +7,5 @@ public class CreateShowDto
     public string? Description { get; set; }
     public string? PyrotechnicImplementationPlan { get; set; }
     public DateTime? Date { get; set; }
+    public int CityId { get; set; }
 }

PyroFetes/DTO/Show/Request/UpdateShowDto.cs

@@ -8,4 +8,5 @@ public class UpdateShowDto
     public string? Description { get; set; }
     public string? PyrotechnicImplementationPlan { get; set; }
     public DateTime? Date { get; set; }
+    public int? CityId { get; set; }
 }

PyroFetes/DTO/Show/Response/ReadShowDto.cs

@@ -8,4 +8,5 @@ public class ReadShowDto
     public string? Description { get; set; }
     public string? PyrotechnicImplementationPlan { get; set; }
     public DateTime? Date { get; set; }
+    public int CityId { get; set; }
 }