feat(market): saved searches with in-app alerts (Wallapop-style)

Save the current market search (query + facets) and get notified when a
matching offer appears in your zone while the app is open, with a catch-up
scan on start. Adds a save affordance in the search bar, a saved-searches
list (apply/delete) with a per-search new-match badge, an AppBar entry
badged with the unseen total, and notification-tap routing to the list.
Alerts evaluate against the user's current area, dedup via seen keys, and
skip own/blocked/hidden/non-active offers. en+es strings.

apps/app_seeds/lib/state/offers_cubit.dart

@@ -267,6 +267,16 @@ class OffersCubit extends Cubit<OffersState> {
   void setHiddenOffers(Set<String> offerKeys) =>
       emit(state.copyWith(hiddenOfferKeys: offerKeys));
 
+  /// Applies a saved search's query and facets to the current discoveries.
+  /// Purely local (does not re-hit the transport) — the area is unchanged, so
+  /// the same discovered offers are simply re-narrowed by the saved filters.
+  void applySavedSearch(SavedSearch search) => emit(state.copyWith(
+        query: search.query,
+        typeFilter: search.types,
+        categoryFilter: search.categories,
+        organicOnly: search.organicOnly,
+      ));
+
   /// Clears every chip filter (leaves the text search untouched).
   void clearFilters() => emit(state.copyWith(
         typeFilter: const {},