Fix collapsed sheets on macOS across the app

Add macOS-only minimum frame sizing to sheets that wrap a
NavigationStack/Form without intrinsic size, so they render properly
instead of collapsing to just the toolbar. Affects Customize Home,
subscription/channel view options, playlist create/edit, search
filters, media browser options, instance picker, log filters, preset
editor, and legacy data import result.

Yattee/Views/Search/SearchView.swift

@@ -1476,6 +1476,9 @@ struct SearchFiltersSheet: View {
                 }
             }
         }
+        #if os(macOS)
+        .frame(minWidth: 500, minHeight: 400)
+        #endif
     }
 }