feat(sales): local sales/purchase ledger (any currency)

A sale is a distinct model from a gift or a Plantare (reproduction
commitment): a recorded seed sale or purchase with an optional price in
ANY currency — €, Ğ1, time, or none yet. Mirrors the Plantare feature.

- schema v10: Sales table (SyncColumns), guarded createTable migration,
  schema dump + generated schema_v10 for the migration round-trip test
- enum SaleDirection { iSold, iBought }
- VarietyRepository: create/watch/watchForVariety/delete + backup
  export/exportForSync/import (LWW-by-HLC, tombstones)
- InventorySnapshot.sales + JSON codec encode/decode (round-trips amount,
  currency, counterparty)
- UI: SalesScreen (/sales), sale sheet, drawer entry, variety-detail
  action beside 'add Plantare'; money hides a trailing .0
- i18n sale block + menu.sales in en/es/pt/ast
- tests: sales repo test (5) incl. Ğ1/price-less/backup round-trip;
  Sales screen added to the small-screen overflow guard

Also harden the overflow guard: swallow the headless engine's image
resource service PNG-decode errors (unrelated to layout) while still
failing on real RenderFlex overflows, so home/about stop reporting
false failures.

apps/app_seeds/lib/data/variety_repository.dart

@@ -1781,6 +1781,64 @@ class VarietyRepository {
     );
   }
 
+  // --- Sales: recorded seed sales (separate from gift/Plantare) --------------
+
+  /// Records a seed sale (or purchase) — price in ANY currency. Returns its id.
+  Future<String> createSale({
+    required SaleDirection direction,
+    String? varietyId,
+    String? counterparty,
+    double? amount,
+    String? currency,
+    String? note,
+  }) async {
+    final (created, updated) = await _stamp();
+    final id = idGen.newId();
+    await _db.into(_db.sales).insert(
+          SalesCompanion.insert(
+            id: id,
+            createdAt: created,
+            updatedAt: updated,
+            lastAuthor: nodeId,
+            direction: direction,
+            varietyId: Value(varietyId),
+            counterparty: Value(counterparty),
+            amount: Value(amount),
+            currency: Value(currency),
+            soldOn: created,
+            note: Value(note),
+          ),
+        );
+    return id;
+  }
+
+  /// All live sales, newest first (for the Sales screen).
+  Stream<List<Sale>> watchSales() => (_db.select(_db.sales)
+        ..where((s) => s.isDeleted.equals(false))
+        ..orderBy([(s) => OrderingTerm.desc(s.soldOn)]))
+      .watch();
+
+  /// The sales recorded against one variety.
+  Stream<List<Sale>> watchSalesForVariety(String varietyId) =>
+      (_db.select(_db.sales)
+            ..where(
+              (s) => s.varietyId.equals(varietyId) & s.isDeleted.equals(false),
+            )
+            ..orderBy([(s) => OrderingTerm.desc(s.soldOn)]))
+          .watch();
+
+  /// Soft-deletes a sale (tombstone, so it syncs as a removal).
+  Future<void> deleteSale(String id) async {
+    final (_, updated) = await _stamp();
+    await (_db.update(_db.sales)..where((s) => s.id.equals(id))).write(
+      SalesCompanion(
+        isDeleted: const Value(true),
+        updatedAt: Value(updated),
+        lastAuthor: Value(nodeId),
+      ),
+    );
+  }
+
   /// Snapshots the live inventory (tombstones excluded) for the interchange
   /// export — data-model §7. Includes photo bytes; the JSON codec embeds them
   /// as base64 and the CSV codec ignores them.
@@ -1819,6 +1877,9 @@ class VarietyRepository {
       plantares: await (_db.select(
         _db.plantares,
       )..where((p) => p.isDeleted.equals(false))).get(),
+      sales: await (_db.select(
+        _db.sales,
+      )..where((s) => s.isDeleted.equals(false))).get(),
     );
   }
 
@@ -1842,6 +1903,7 @@ class VarietyRepository {
       movements: await _db.select(_db.movements).get(),
       parties: await _db.select(_db.parties).get(),
       plantares: await _db.select(_db.plantares).get(),
+      sales: await _db.select(_db.sales).get(),
       // attachments intentionally omitted — photos don't ride the sync wire.
     );
   }
@@ -1942,6 +2004,14 @@ class VarietyRepository {
         updatedAtOf: (r) => r.updatedAt,
         reconciler: reconciler,
       );
+      summary += await _importMutableRows(
+        table: _db.sales,
+        idColumn: _db.sales.id,
+        rows: snapshot.sales,
+        idOf: (r) => r.id,
+        updatedAtOf: (r) => r.updatedAt,
+        reconciler: reconciler,
+      );
       summary += await _importMovements(snapshot.movements, reconciler);
     });
 
@@ -1955,6 +2025,7 @@ class VarietyRepository {
       for (final p in snapshot.parties) p.updatedAt,
       for (final a in snapshot.attachments) a.updatedAt,
       for (final pl in snapshot.plantares) pl.updatedAt,
+      for (final s in snapshot.sales) s.updatedAt,
     ]);
     if (maxIncoming != null) {
       _clock = _clock.receiveEvent(maxIncoming, _now());