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/CreateShowEndpoint.cs

@@ -16,11 +16,12 @@ public class CreateShowEndpoint(PyroFetesDbContext pyroFetesDbContext) : Endpoin
     {
         var show = new PyroFetes.Models.Show
         {
-            Name = req.Name,
-            Place = req.Place,
+            Name = req.Name ?? string.Empty,
+            Place = req.Place ?? string.Empty,
             Description = req.Description,
-            PyrotechnicImplementationPlan = req.PyrotechnicImplementationPlan,
-            Date = req.Date.HasValue ? DateOnly.FromDateTime(req.Date.Value) : null
+            PyrotechnicImplementationPlan = req.PyrotechnicImplementationPlan ?? string.Empty,
+            Date = req.Date.HasValue ? DateOnly.FromDateTime(req.Date.Value) : null,
+            CityId = req.CityId
         };
 
         pyroFetesDbContext.Shows.Add(show);
@@ -33,7 +34,8 @@ public class CreateShowEndpoint(PyroFetesDbContext pyroFetesDbContext) : Endpoin
             Place = show.Place,
             Description = show.Description,
             PyrotechnicImplementationPlan = show.PyrotechnicImplementationPlan,
-            Date = show.Date.HasValue ? show.Date.Value.ToDateTime(TimeOnly.MinValue) : null
+            Date = show.Date.HasValue ? show.Date.Value.ToDateTime(TimeOnly.MinValue) : null,
+            CityId = show.CityId
         };
 
         await Send.OkAsync(result, ct);