feat(market): fix publish-duplicates, add offer detail page + filters

The vecino/market view had three gaps:

- Publishing inventory duplicated the listing. discover() appended every
  offer the relay streamed, but relays legitimately resend an addressable
  NIP-99 event (stored copy + live echo on publish). Merge by
  (authorPubkeyHex, id) so each offer appears once; two authors reusing a
  lot id stay distinct.
- No product detail. Tapping a card jumped straight to chat. Add a
  read-only "product page" (MarketOfferDetailScreen) with title, mode,
  category, eco badge, coarse location, price, a "Shared by" seller
  section (profile fetched by pubkey) and the message button. Reached via
  a new /market/offer route; cards are now fully tappable. Shows only what
  the network already carries — no photos/description added to the wire.
- No filters. Add a filter bar (type, category, eco) mirroring inventory,
  each chip group shown only when a discovered offer can match it. To make
  the eco filter real, publish the organic flag on the wire: Offer.isOrganic
  -> NIP-99 'organic' tag -> OfferMapper -> ShareableLot.

Tests: commons_core organic round-trip; app-side dedup, two-author
separation, filter logic, mapper passthrough; detail-screen widget tests.
i18n keys added to en/es/pt/ast and slang regenerated.

apps/app_seeds/lib/data/variety_repository.dart

@@ -128,6 +128,7 @@ class ShareableLot extends Equatable {
     required this.offerStatus,
     this.category,
     this.harvestYear,
+    this.isOrganic = false,
   });
 
   final String lotId;
@@ -140,8 +141,13 @@ class ShareableLot extends Equatable {
   final String? category;
   final int? harvestYear;
 
+  /// The variety's grower-declared organic ("eco") flag, published so peers can
+  /// filter the market for it.
+  final bool isOrganic;
+
   @override
-  List<Object?> get props => [lotId, summary, offerStatus, category, harvestYear];
+  List<Object?> get props =>
+      [lotId, summary, offerStatus, category, harvestYear, isOrganic];
 }
 
 /// One germination test on a lot; [rate] is derived (0..1), null when it can't
@@ -1269,6 +1275,7 @@ class VarietyRepository {
             offerStatus: l.offerStatus,
             category: v.category,
             harvestYear: l.harvestYear,
+            isOrganic: v.isOrganic,
           ),
     ];
   }