[mobile][photos] Improve magic section UX (#3235)

## Description

Check commits. 


https://github.com/user-attachments/assets/07f8aeec-163d-4ef7-b7f5-e78a475d364d



## Tests

Tested all changes.

mobile/lib/events/magic_sort_change_event.dart

@@ -0,0 +1,11 @@
+import "package:photos/events/event.dart";
+
+enum MagicSortType {
+  mostRecent,
+  mostRelevant,
+}
+
+class MagicSortChangeEvent extends Event {
+  final MagicSortType sortType;
+  MagicSortChangeEvent(this.sortType);
+}