[#43] App: Use FileSystemWatcher to renew contexts on demand

Elwig/Windows/SeasonFinishWindow.xaml.cs

@@ -19,7 +19,7 @@ namespace Elwig.Windows {
             SeasonInput.Value = Utils.CurrentLastSeason;
         }
 
-        protected override Task OnRenewContext() {
+        protected override Task OnRenewContext(AppDbContext ctx) {
             SeasonInput_ValueChanged(null, null);
             return Task.CompletedTask;
         }