feat(plantare): usable UI — commitments screen, add sheet, entry points

The reproduction-commitment (Plantare) UI, local-first and plain-spoken:
- A Plantares screen (drawer entry, /plantares) listing your commitments,
  grouped Open / Done, with a big 'mark returned', a menu (let it go / reopen
  / remove) and an empty-state that explains what a Plantare is.
- An add sheet (scrollable): a two-choice 'who reproduces & returns' (I return
  / owed to me), an optional 'with whom', an optional 'what comes back' in the
  grower's own words, and a note. No sale, no currency — a promise.
- Reachable from a seed too: an 'Add a commitment' action on the variety
  detail, pre-attached to that variety.
- i18n en/es/pt/ast (human words: 'Plantare' + a plain explanation).

Added the Plantares screen to the small-phone overflow guard (18 cases green).

apps/app_seeds/lib/ui/variety_detail_screen.dart

@@ -16,6 +16,7 @@ import '../i18n/strings.g.dart';
 import '../state/variety_detail_cubit.dart';
 import 'harvest_date_picker.dart';
 import 'photo_pick.dart';
+import 'plantare_sheet.dart';
 import 'quantity_kind_l10n.dart';
 import 'quantity_picker.dart';
 import 'seed_glyph.dart';
@@ -108,6 +109,21 @@ class _DetailView extends StatelessWidget {
               ),
             ],
           ),
+          const SizedBox(height: 16),
+          _SectionTitle(t.plantare.title),
+          Align(
+            alignment: AlignmentDirectional.centerStart,
+            child: OutlinedButton.icon(
+              key: const Key('detail.addPlantare'),
+              icon: const Icon(Icons.volunteer_activism_outlined, size: 18),
+              onPressed: () => showPlantareSheet(
+                context,
+                repository: context.read<VarietyRepository>(),
+                varietyId: detail.id,
+              ),
+              label: Text(t.plantare.add),
+            ),
+          ),
           if (detail.notes != null && detail.notes!.trim().isNotEmpty) ...[
             const SizedBox(height: 16),
             _SectionTitle(t.detail.notes),