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/UpdateShowEndpoint.cs

@@ -35,7 +35,7 @@ public class UpdateShowEndpoint(PyroFetesDbContext pyroFetesDbContext) : Endpoin
         show.Description = req.Description ?? show.Description;
         show.PyrotechnicImplementationPlan = req.PyrotechnicImplementationPlan ?? show.PyrotechnicImplementationPlan;
         if (req.CityId.HasValue) show.CityId = req.CityId.Value;
-        if (req.Date.HasValue) show.Date = DateOnly.FromDateTime(req.Date.Value);
+        if (req.Date.HasValue) show.Date = req.Date.Value;
 
         await pyroFetesDbContext.SaveChangesAsync(ct);
 
@@ -46,7 +46,7 @@ public class UpdateShowEndpoint(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
         };