feat(labels): choose copies per label, prefilled from container count

Each label in the print sheet gets an editable copy count, suggested from
the lot's latest condition-check container count (3 jars → 3 labels), and
falling back to 1. Type or step the count; the total updates live and Save
is disabled at zero. On save each seed expands into that many identical
labels.

- SeedLabelEntry.suggestedCopies; labelRows reads the latest container count
- label print sheet: per-row −/number/+ stepper, live total, expand on save
- tests: repository suggestedCopies + print-sheet copy chooser

apps/app_seeds/test/ui/label_print_sheet_test.dart

@@ -0,0 +1,97 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/data/variety_repository.dart';
+import 'package:tane/i18n/strings.g.dart';
+import 'package:tane/ui/label_print_sheet.dart';
+
+/// Hosts a button that opens the print-labels sheet for [entries].
+Widget _host(List<SeedLabelEntry> entries) {
+  LocaleSettings.setLocaleSync(AppLocale.en);
+  return TranslationProvider(
+    child: MaterialApp(
+      supportedLocales: AppLocaleUtils.supportedLocales,
+      localizationsDelegates: const [
+        GlobalMaterialLocalizations.delegate,
+        GlobalWidgetsLocalizations.delegate,
+        GlobalCupertinoLocalizations.delegate,
+      ],
+      home: Scaffold(
+        body: Builder(
+          builder: (context) => ElevatedButton(
+            onPressed: () => showLabelPrintSheet(context, entries),
+            child: const Text('Open'),
+          ),
+        ),
+      ),
+    ),
+  );
+}
+
+void main() {
+  Future<void> open(WidgetTester tester) async {
+    await tester.tap(find.text('Open'));
+    await tester.pumpAndSettle();
+  }
+
+  testWidgets('prefills copies from the suggested count and totals them', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      _host(const [
+        SeedLabelEntry(varietyLabel: 'Tomate', suggestedCopies: 3),
+        SeedLabelEntry(varietyLabel: 'Alubia', suggestedCopies: 1),
+      ]),
+    );
+    await open(tester);
+
+    // 3 + 1 suggested = 4 labels.
+    expect(find.text('4 labels'), findsOneWidget);
+  });
+
+  testWidgets('the stepper and the field both edit a copy count', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      _host(const [
+        SeedLabelEntry(varietyLabel: 'Tomate', suggestedCopies: 3),
+        SeedLabelEntry(varietyLabel: 'Alubia', suggestedCopies: 1),
+      ]),
+    );
+    await open(tester);
+
+    await tester.tap(
+      find.byKey(const Key('printLabels.copies.minus.Tomate')),
+    );
+    await tester.pumpAndSettle();
+    expect(find.text('3 labels'), findsOneWidget); // 2 + 1
+
+    await tester.enterText(
+      find.byKey(const Key('printLabels.copies.field.Tomate')),
+      '5',
+    );
+    await tester.pumpAndSettle();
+    expect(find.text('6 labels'), findsOneWidget); // 5 + 1
+  });
+
+  testWidgets('saving is disabled when the total is zero', (tester) async {
+    await tester.pumpWidget(
+      _host(const [
+        SeedLabelEntry(varietyLabel: 'Tomate', suggestedCopies: 1),
+      ]),
+    );
+    await open(tester);
+
+    await tester.enterText(
+      find.byKey(const Key('printLabels.copies.field.Tomate')),
+      '0',
+    );
+    await tester.pumpAndSettle();
+    expect(find.text('0 labels'), findsOneWidget);
+
+    final save = tester.widget<FilledButton>(
+      find.byKey(const Key('printLabels.save')),
+    );
+    expect(save.onPressed, isNull);
+  });
+}