feat(inventory): editable vernacular (common) names

The "also known as" names were read-only; now they can be added and removed:
- Repository: addVernacularName + removeVernacularName (soft delete);
  VarietyDetail.vernacularNames carries ids (new VernacularName model).
- Cubit: addVernacularName / removeVernacularName.
- Detail: deletable name chips + an "Add name" chip opening a small dialog;
  the section is always visible so names can be added when empty.

Tests: repo add/remove + widget add/remove. 44 green.

apps/app_seeds/test/ui/variety_detail_screen_test.dart

@@ -255,4 +255,32 @@ void main() {
     expect(find.text('No lots yet.'), findsOneWidget);
     await disposeTree(tester);
   });
+
+  testWidgets('adding and removing a vernacular name', (tester) async {
+    final repo = newTestRepository(db);
+    final id = await repo.addQuickVariety(label: 'Maize');
+
+    await tester.pumpWidget(
+      wrapDetail(
+        repository: repo,
+        varietyId: id,
+        species: newTestSpeciesRepository(db),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    await tester.tap(find.byKey(const Key('name.add')));
+    await tester.pumpAndSettle();
+    await tester.enterText(find.byKey(const Key('name.field')), 'Maíz');
+    await tester.tap(find.byKey(const Key('name.save')));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Maíz'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.close)); // the chip's delete icon
+    await tester.pumpAndSettle();
+
+    expect(find.text('Maíz'), findsNothing);
+    await disposeTree(tester);
+  });
 }