feat(seed-saving): per-crop 'how to save this seed' guidance

A bundled, curated knowledge layer — the differentiator of a serious
seed app. For a variety's crop it shows how the plant reproduces and what
it takes to keep the variety true: life cycle, pollination (self/cross +
insect/wind), isolation distance, how many plants to save from, dry/wet
processing, a difficulty pill, and a short tip — all in human words.

- assets/catalog/seed_saving.json: curated public-domain data (Seed to
  Seed / Seed Savers), keyed by botanical FAMILY (defaults) with
  per-species/genus OVERRIDES that win — so e.g. Vicia faba is correctly
  insect-cross-pollinated despite the selfing Fabaceae default, and maize
  is wind-pollinated with a large population. Notes are locale-keyed
  (es/en), extensible to any language — a starter set, not a ceiling.
- domain/seed_saving.dart (pure): enums + SeedSavingGuide (merge, note
  fallback) + SeedSavingData.guideFor (species → genus → family).
- data/seed_saving_catalog.dart: loads the asset once into an in-memory
  singleton (no DB table, no migration); injector loads it at startup.
- VarietyDetail gains  (from the linked species — the reliable
  key, vs the editable category); detail screen shows a _SeedSavingView
  when a guide resolves.
- i18n seedSaving block (labels + enum values + params) in en/es/pt/ast.
- Tests: domain lookup/merge, the real asset's key corrections, and the
  detail section shows/hides. 314 suite tests green; analyze clean.

apps/app_seeds/test/data/seed_saving_asset_test.dart

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+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/domain/seed_saving.dart';
+
+/// Guards the committed bundled seed-saving asset: it must parse, cover the
+/// major families, and carry the notable per-species corrections the UI relies
+/// on. Reads the file directly — no Flutter asset bundle — so it runs as a
+/// plain VM test.
+void main() {
+  final data =
+      parseSeedSaving(File('assets/catalog/seed_saving.json').readAsStringSync());
+
+  test('resolves the major families', () {
+    for (final family in const [
+      'Solanaceae',
+      'Fabaceae',
+      'Cucurbitaceae',
+      'Brassicaceae',
+      'Asteraceae',
+      'Apiaceae',
+      'Amaranthaceae',
+      'Poaceae',
+    ]) {
+      expect(data.guideFor(family: family)?.hasAny, isTrue, reason: family);
+    }
+  });
+
+  test('faba bean is corrected to insect cross-pollination', () {
+    // The whole point of species overrides: unlike other legumes, Vicia faba
+    // crosses — the guidance must not inherit Fabaceae "self".
+    final g = data.guideFor(scientificName: 'Vicia faba', family: 'Fabaceae');
+    expect(g?.pollination, Pollination.cross);
+    expect(g?.vector, PollinationVector.insect);
+    expect(g?.noteFor('es'), isNotNull);
+  });
+
+  test('tomato self-pollinates and is wet-processed', () {
+    final g = data.guideFor(
+        scientificName: 'Solanum lycopersicum', family: 'Solanaceae');
+    expect(g?.pollination, Pollination.self);
+    expect(g?.processing, SeedProcessing.wet);
+    expect(g?.difficulty, SavingDifficulty.easy);
+  });
+
+  test('maize is wind-pollinated with a large population', () {
+    final g = data.guideFor(scientificName: 'Zea mays', family: 'Poaceae');
+    expect(g?.vector, PollinationVector.wind);
+    expect(g?.recommendedPlants, greaterThanOrEqualTo(50));
+  });
+}

apps/app_seeds/test/domain/seed_saving_test.dart

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+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/domain/seed_saving.dart';
+
+/// Pure lookup/merge logic for the seed-saving guidance: a per-species entry
+/// overrides its family default, a bare genus is a fallback, and unknown crops
+/// resolve to null.
+void main() {
+  final data = parseSeedSaving('''
+  {
+    "families": {
+      "Fabaceae": { "lifeCycle": "annual", "pollination": "self", "processing": "dry", "difficulty": "easy" },
+      "Solanaceae": { "pollination": "self", "isolationMinM": 3, "isolationMaxM": 15 }
+    },
+    "species": {
+      "Vicia faba": { "pollination": "cross", "vector": "insect", "isolationMinM": 180, "note": {"es": "aísla", "en": "isolate"} },
+      "Cucurbita": { "pollination": "cross", "vector": "insect" }
+    }
+  }
+  ''');
+
+  test('a species entry overrides its family default', () {
+    final g = data.guideFor(scientificName: 'Vicia faba', family: 'Fabaceae');
+    expect(g, isNotNull);
+    // Family said self+easy+annual; the species override flips pollination.
+    expect(g!.pollination, Pollination.cross);
+    expect(g.vector, PollinationVector.insect);
+    expect(g.isolationMinM, 180);
+    // Fields the species didn't set fall through to the family.
+    expect(g.lifeCycle, LifeCycle.annual);
+    expect(g.difficulty, SavingDifficulty.easy);
+    expect(g.processing, SeedProcessing.dry);
+  });
+
+  test('a bare genus key is a fallback when the species is unlisted', () {
+    final g = data.guideFor(scientificName: 'Cucurbita maxima', family: null);
+    expect(g?.pollination, Pollination.cross);
+    expect(g?.vector, PollinationVector.insect);
+  });
+
+  test('family-only lookup returns the family default', () {
+    final g = data.guideFor(family: 'Solanaceae');
+    expect(g?.pollination, Pollination.self);
+    expect(g?.isolationMaxM, 15);
+  });
+
+  test('lookup is case-insensitive', () {
+    expect(data.guideFor(family: 'fabaceae'), isNotNull);
+    expect(data.guideFor(scientificName: 'vicia faba'), isNotNull);
+  });
+
+  test('an unknown crop resolves to null', () {
+    expect(data.guideFor(scientificName: 'Musa acuminata', family: 'Musaceae'),
+        isNull);
+  });
+
+  test('noteFor falls back to English then any language', () {
+    final g = data.guideFor(scientificName: 'Vicia faba')!;
+    expect(g.noteFor('es'), 'aísla');
+    expect(g.noteFor('fr'), 'isolate'); // no fr → en
+  });
+
+  test('mergedWith unions notes with the override winning', () {
+    const base = SeedSavingGuide(note: {'es': 'a', 'en': 'b'});
+    const over = SeedSavingGuide(note: {'es': 'c'});
+    expect(base.mergedWith(over).note, {'es': 'c', 'en': 'b'});
+  });
+}

apps/app_seeds/test/ui/seed_saving_section_test.dart

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+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/data/seed_saving_catalog.dart';
+import 'package:tane/db/database.dart';
+import 'package:tane/domain/seed_saving.dart';
+
+import '../support/test_support.dart';
+
+/// The variety detail shows "how to save this seed" when the bundled catalog
+/// has guidance for the crop's family, and hides it otherwise.
+void main() {
+  late AppDatabase db;
+  setUp(() {
+    db = newTestDatabase();
+    SeedSavingCatalog.data = parseSeedSaving('''
+    {
+      "families": {
+        "Solanaceae": { "pollination": "self", "isolationMinM": 3, "isolationMaxM": 6, "processing": "wet", "difficulty": "easy" }
+      },
+      "species": {}
+    }
+    ''');
+  });
+  tearDown(() {
+    SeedSavingCatalog.data = null;
+    return db.close();
+  });
+
+  Future<void> pumpDetailFor(WidgetTester tester, String? category) async {
+    final repo = newTestRepository(db);
+    final id = await repo.addQuickVariety(label: 'Tomate', category: category);
+    await tester.pumpWidget(wrapDetail(repository: repo, varietyId: id));
+    await tester.pumpAndSettle();
+  }
+
+  testWidgets('shows the seed-saving section for a known family', (tester) async {
+    await pumpDetailFor(tester, 'Solanaceae');
+
+    expect(find.text('Saving its seed'), findsOneWidget);
+    // The pollination line is a Text.rich (label + value), so match the run.
+    expect(find.textContaining('Self-pollinating'), findsOneWidget);
+    expect(find.text('Easy'), findsOneWidget); // the difficulty pill
+
+    await disposeTree(tester);
+  });
+
+  testWidgets('hides the section when nothing matches', (tester) async {
+    await pumpDetailFor(tester, 'Unknownaceae');
+
+    expect(find.text('Saving its seed'), findsNothing);
+
+    await disposeTree(tester);
+  });
+}