refactor(feed): re-add optional savedFilter to filter applied event

Re-introduces the optional `savedFilter` property to the `HeadlinesFeedFiltersApplied` event.

This change is a targeted fix to resolve a race condition that occurs when a new filter is saved and immediately applied. By passing the newly created `SavedFilter` object directly, the `HeadlinesFeedBloc` can deterministically set the active filter ID without relying on its internal list of saved filters, which may not have been updated yet.

Author: fulleni

lib/headlines-feed/bloc/headlines_feed_event.dart

@@ -52,28 +52,35 @@ final class HeadlinesFeedRefreshRequested extends HeadlinesFeedEvent {
 /// Event triggered when a new set of filters, selected by the user,
 /// should be applied to the headlines feed.
 /// {@endtemplate}
-///
-/// The `activeFilterId` is now determined within the `HeadlinesFeedBloc` by
-/// comparing the applied filter against the list of saved filters. This makes
-/// passing a `savedFilter` object on this event redundant.
+/// The `activeFilterId` is determined within the `HeadlinesFeedBloc`.
+/// In most cases, this is done by comparing the applied filter against the
+/// list of saved filters. However, to prevent a race condition during the
+/// "save and apply" flow, an optional `savedFilter` can be provided to
+/// ensure the newly created filter is selected immediately.
 final class HeadlinesFeedFiltersApplied extends HeadlinesFeedEvent {
   /// {@macro headlines_feed_filters_applied}
   ///
   /// Contains the complete [HeadlineFilter] configuration to be applied.
   const HeadlinesFeedFiltersApplied({
     required this.filter,
     required this.adThemeStyle,
+    this.savedFilter,
   });
 
   /// The [HeadlineFilter] containing the selected categories, sources,
   /// and/or countries.
   final HeadlineFilter filter;
 
+  /// The optional [SavedFilter] that this filter corresponds to.
+  /// This is used exclusively during the "save and apply" flow to prevent
+  /// a race condition and ensure the new filter's chip is selected.
+  final SavedFilter? savedFilter;
+
   /// The current ad theme style of the application.
   final AdThemeStyle adThemeStyle;
 
   @override
-  List<Object?> get props => [filter, adThemeStyle];
+  List<Object?> get props => [filter, adThemeStyle, savedFilter];
 }
 
 /// {@template headlines_feed_filters_cleared}