fix: register PushNotificationService as scoped, not singleton

PushNotificationService injects TimePlanningPnDbContext (scoped) and
reads from it in the constructor. A singleton registration causes
"Cannot consume scoped service from singleton" at startup. Change to
AddScoped so it gets a fresh DbContext per request.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: renemadsen

eFormAPI/Plugins/TimePlanning.Pn/TimePlanning.Pn/EformTimePlanningPlugin.cs

@@ -110,7 +110,7 @@ public void ConfigureServices(IServiceCollection services)
         services.AddTransient<IPayTimeBandRuleService, PayTimeBandRuleService>();
         services.AddTransient<IPayrollExportService, PayrollExportService>();
         services.AddTransient<IDeviceTokenService, DeviceTokenService>();
-        services.AddSingleton<IPushNotificationService, PushNotificationService>();
+        services.AddScoped<IPushNotificationService, PushNotificationService>();
         services.AddControllers();
     }