New clear all button in recent pages

First-time open of app correctly shows Welcome page
New Home button in group and entry pages

ModernKeePass/Interfaces/IRecent.cs

@@ -10,5 +10,6 @@ namespace ModernKeePass.Interfaces
         Task<IStorageItem> GetFileAsync(string token);
         ObservableCollection<IRecentItem> GetAllFiles(bool removeIfNonExistant = true);
         void Add(IStorageItem file, string metadata);
+        void ClearAll();
     }
 }