db: Add source to items

This also adds the missing update fields for mediums and albums.

data/ui/editor/album.blp

@@ -65,9 +65,15 @@ template $MusicusAlbumEditor: Adw.NavigationPage {
             margin-top: 24;
 
             styles [
-              "boxed-list",
+              "boxed-list-separate",
             ]
 
+            Adw.SwitchRow enable_updates_row {
+              title: _("Enable updates");
+              subtitle: _("Keep this item up to date with the online metadata library");
+              active: true;
+            }
+
             Adw.ButtonRow save_row {
               title: _("_Create album");
               use-underline: true;