refactor(feed): remove savedFilter from HeadlinesFeedFiltersApplied event

Removes the `savedFilter` property from the `HeadlinesFeedFiltersApplied` event.

The logic for determining the active filter ID (whether it's a saved filter or a new 'custom' one) is being centralized within the `HeadlinesFeedBloc`. The bloc will now compare the incoming filter against the list of saved filters, making this property redundant and simplifying the event's API.

Author: fulleni

lib/headlines-feed/bloc/headlines_feed_event.dart

@@ -52,30 +52,28 @@ 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.
 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 to correctly set the active filter ID when a new
-  /// filter is saved and immediately applied.
-  final SavedFilter? savedFilter;
-
   /// The current ad theme style of the application.
   final AdThemeStyle adThemeStyle;
 
   @override
-  List<Object?> get props => [filter, adThemeStyle, savedFilter];
+  List<Object?> get props => [filter, adThemeStyle];
 }
 
 /// {@template headlines_feed_filters_cleared}