Migrate Show.Date from DateOnly to DateTime to support time of day

Removes DateOnly/DateTime conversion boilerplate from all Show endpoints
and adds the corresponding EF Core migration.

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

PyroFetes/Endpoints/Show/CreateShowEndpoint.cs

@@ -20,7 +20,7 @@ public class CreateShowEndpoint(PyroFetesDbContext pyroFetesDbContext) : Endpoin
             Place = req.Place ?? string.Empty,
             Description = req.Description,
             PyrotechnicImplementationPlan = req.PyrotechnicImplementationPlan ?? string.Empty,
-            Date = req.Date.HasValue ? DateOnly.FromDateTime(req.Date.Value) : null,
+            Date = req.Date,
             CityId = req.CityId
         };
 
@@ -34,7 +34,7 @@ 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,
             CityId = show.CityId
         };