feat(social): add SavedSearch model with shared offer matcher

Extract the market's query/type/category/organic filter chain into
SavedSearch.matchesFilters so live results and saved-search alerts can
never disagree. OffersState.visibleOffers now delegates to it.

packages/commons_core/lib/commons_core.dart

@@ -35,6 +35,7 @@ export 'src/social/profile_transport.dart';
 export 'src/social/rating.dart';
 export 'src/social/rating_transport.dart';
 export 'src/social/report_transport.dart';
+export 'src/social/saved_search.dart';
 export 'src/social/sync_transport.dart';
 export 'src/social/trust_transport.dart';
 export 'src/social/web_of_trust.dart';

packages/commons_core/lib/src/social/saved_search.dart

@@ -0,0 +1,124 @@
+import 'package:equatable/equatable.dart';
+
+import 'offer.dart';
+
+/// A person's saved market search — the query and facets they want to be
+/// alerted about, Wallapop's "búsquedas favoritas". Generic core type: it knows
+/// how to decide whether an [Offer] matches, but nothing about seeds.
+///
+/// The filter chain mirrors the market screen's live filtering exactly (same
+/// case-insensitive summary match, same ANDed facets), so a saved search and
+/// the on-screen results can never disagree. Moderation state (blocked authors,
+/// hidden offers, the user's own listings) is deliberately NOT part of a search
+/// — the app layer applies that on top.
+class SavedSearch extends Equatable {
+  const SavedSearch({
+    required this.id,
+    required this.label,
+    this.query = '',
+    this.types = const {},
+    this.categories = const {},
+    this.organicOnly = false,
+    this.createdAt = 0,
+  });
+
+  /// Stable per-search identifier (a UUID from the app's IdGen).
+  final String id;
+
+  /// Human name for the search, shown in the list (e.g. "Tomates cerca").
+  final String label;
+
+  /// Free-text filter over the offer summary; empty = no text constraint.
+  final String query;
+
+  /// Reciprocity-mode facet (gift/exchange/sale/wanted); empty = any type.
+  final Set<OfferType> types;
+
+  /// Category facet (free-text categories); empty = any category.
+  final Set<String> categories;
+
+  /// When true, only offers the grower declared organic ("eco") match.
+  final bool organicOnly;
+
+  /// Creation time (ms since epoch), for stable newest-first ordering.
+  final int createdAt;
+
+  /// Whether [offer] satisfies this search's query and facets (all ANDed).
+  /// Same semantics the market screen uses for its visible list.
+  bool matches(Offer offer) => matchesFilters(
+        offer,
+        query: query,
+        types: types,
+        categories: categories,
+        organicOnly: organicOnly,
+      );
+
+  /// The shared, pure filter chain used by both the market screen's live
+  /// results and saved-search alerts, so the two paths can't drift.
+  static bool matchesFilters(
+    Offer offer, {
+    String query = '',
+    Set<OfferType> types = const {},
+    Set<String> categories = const {},
+    bool organicOnly = false,
+  }) {
+    final q = query.trim().toLowerCase();
+    if (q.isNotEmpty && !offer.summary.toLowerCase().contains(q)) return false;
+    if (types.isNotEmpty && !types.contains(offer.type)) return false;
+    if (categories.isNotEmpty &&
+        (offer.category == null || !categories.contains(offer.category))) {
+      return false;
+    }
+    if (organicOnly && !offer.isOrganic) return false;
+    return true;
+  }
+
+  SavedSearch copyWith({
+    String? id,
+    String? label,
+    String? query,
+    Set<OfferType>? types,
+    Set<String>? categories,
+    bool? organicOnly,
+    int? createdAt,
+  }) {
+    return SavedSearch(
+      id: id ?? this.id,
+      label: label ?? this.label,
+      query: query ?? this.query,
+      types: types ?? this.types,
+      categories: categories ?? this.categories,
+      organicOnly: organicOnly ?? this.organicOnly,
+      createdAt: createdAt ?? this.createdAt,
+    );
+  }
+
+  Map<String, dynamic> toJson() => {
+        'id': id,
+        'label': label,
+        if (query.isNotEmpty) 'query': query,
+        if (types.isNotEmpty) 'types': [for (final t in types) t.name],
+        if (categories.isNotEmpty) 'categories': categories.toList(),
+        if (organicOnly) 'organicOnly': true,
+        'createdAt': createdAt,
+      };
+
+  factory SavedSearch.fromJson(Map<String, dynamic> json) => SavedSearch(
+        id: json['id'] as String,
+        label: json['label'] as String,
+        query: json['query'] as String? ?? '',
+        types: {
+          for (final t in (json['types'] as List? ?? const []))
+            OfferType.values.byName(t as String),
+        },
+        categories: {
+          for (final c in (json['categories'] as List? ?? const [])) c as String,
+        },
+        organicOnly: json['organicOnly'] as bool? ?? false,
+        createdAt: json['createdAt'] as int? ?? 0,
+      );
+
+  @override
+  List<Object?> get props =>
+      [id, label, query, types, categories, organicOnly, createdAt];
+}