feat(inventory): local sharing — per-lot share terms, filter and printable catalog

The local half of the original Fase 2 (no network, no Offer entity yet):
- Lot sheet gains a 'do you share it?' choice (gift/swap first, sale last,
  never the default); declaring plenty of abundance reveals it with a nudge.
- Lot lines and list tiles badge shared batches; an 'I share' filter and
  a printable PDF catalog (paper bridge for fairs) round out the view.
- Catalog PDF embeds DejaVu (Latin-ext/Cyrillic/Greek); fonts are a
  per-locale resource like the OCR packs.

apps/app_seeds/test/services/share_catalog_service_test.dart

@@ -0,0 +1,66 @@
+import 'dart:typed_data';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/services/file_service.dart';
+import 'package:tane/services/share_catalog_service.dart';
+
+/// Captures the bytes handed to the save dialog instead of touching disk.
+class _RecordingFileService implements FileService {
+  Uint8List? saved;
+  String? savedName;
+
+  @override
+  Future<String?> saveFile({
+    required String suggestedName,
+    required Uint8List bytes,
+  }) async {
+    saved = bytes;
+    savedName = suggestedName;
+    return '/dev/null/$suggestedName';
+  }
+
+  @override
+  Future<Uint8List?> pickFileBytes({List<String>? allowedExtensions}) async =>
+      null;
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  test('buildPdf renders a well-formed PDF with the given rows', () async {
+    final service = ShareCatalogService(files: _RecordingFileService());
+    final bytes = await service.buildPdf(
+      title: 'What I share',
+      date: 'July 9, 2026',
+      rows: const [
+        ShareCatalogRow(
+          name: 'Rebordanes maize',
+          scientificName: 'Zea mays',
+          details: 'Seeds · Year 2024 · 2 cobs',
+          mode: 'To give away',
+        ),
+        ShareCatalogRow(name: 'Alubia de Tolosa', mode: 'To swap'),
+      ],
+    );
+
+    // %PDF header + non-trivial body; text content is compressed, so the
+    // human-readable row assertions live in the widget/data tests.
+    expect(String.fromCharCodes(bytes.take(5)), '%PDF-');
+    expect(bytes.length, greaterThan(1000));
+  });
+
+  test('saveCatalog hands the PDF to the save dialog', () async {
+    final files = _RecordingFileService();
+    final service = ShareCatalogService(files: files);
+    final saved = await service.saveCatalog(
+      title: 'What I share',
+      date: 'July 9, 2026',
+      suggestedName: 'tanemaki-catalog-2026-07-09.pdf',
+      rows: const [ShareCatalogRow(name: 'Maize', mode: 'To give away')],
+    );
+
+    expect(saved, isTrue);
+    expect(files.savedName, 'tanemaki-catalog-2026-07-09.pdf');
+    expect(String.fromCharCodes(files.saved!.take(5)), '%PDF-');
+  });
+}