feat(species): derived verified reference links (GBIF/Wikipedia/Wikispecies)

Add a read-only "Learn more" section on the variety detail that surfaces
verified external references for the linked species, built deterministically
from bundled identifiers — no titles bundled, no network, offline-first:

- GBIF taxon page from the backbone key
- Wikipedia via Wikidata Special:GoToLinkedPage (locale-aware, RTL-safe,
  falls back to the Wikidata item when a language lacks the article)
- Wikispecies from the scientific name

Enrich the bundled catalog (species.json v3) with gbif_key + wikidata_qid for
all 14 species, cross-checked (each QID carries GBIF ID P846 = the key).
Schema already had the columns; seedBundled now persists and backfills them.

The grower's own manual links stay but are demoted (progressive disclosure):
the section only shows when links exist and "Add link" is a low-emphasis
button, since hand-adding a link is the rarer power move.

Pure-Dart link builder is unit-tested; repo persistence/backfill and the
detail-screen section are covered too.

apps/app_seeds/test/data/species_repository_test.dart

@@ -1,4 +1,5 @@
 import 'package:commons_core/commons_core.dart';
+import 'package:drift/drift.dart' show Value;
 import 'package:flutter_test/flutter_test.dart';
 import 'package:tane/data/species_catalog.dart';
 import 'package:tane/data/species_repository.dart';
@@ -49,6 +50,65 @@ void main() {
     },
   );
 
+  test('parseSpeciesCatalog reads gbif and wikidata identifiers', () {
+    const json = '''
+    {"version":3,"species":[
+      {"scientific_name":"Zea mays","gbif_key":5290052,"wikidata_qid":"Q11575"},
+      {"scientific_name":"Unknown sp."}
+    ]}''';
+    final seeds = parseSpeciesCatalog(json);
+    expect(seeds.first.gbifKey, 5290052);
+    expect(seeds.first.wikidataQid, 'Q11575');
+    // Missing identifiers stay null, they are optional.
+    expect(seeds.last.gbifKey, isNull);
+    expect(seeds.last.wikidataQid, isNull);
+  });
+
+  test('seedBundled persists gbif and wikidata identifiers', () async {
+    await repo.seedBundled(const [
+      SpeciesSeed(
+        scientificName: 'Zea mays',
+        gbifKey: 5290052,
+        wikidataQid: 'Q11575',
+      ),
+    ]);
+    final row = await db.select(db.species).getSingle();
+    expect(row.gbifKey, 5290052);
+    expect(row.wikidataQid, 'Q11575');
+  });
+
+  test(
+    'seedBundled backfills identifiers onto rows seeded before them',
+    () async {
+      // A pre-existing bundled row that predates the identifier fields.
+      await db
+          .into(db.species)
+          .insert(
+            SpeciesCompanion.insert(
+              id: 'legacy',
+              createdAt: 0,
+              updatedAt: '0',
+              lastAuthor: 'bundle',
+              scientificName: 'Zea mays',
+              isBundled: const Value(true),
+            ),
+          );
+
+      await repo.seedBundled(const [
+        SpeciesSeed(
+          scientificName: 'Zea mays',
+          gbifKey: 5290052,
+          wikidataQid: 'Q11575',
+        ),
+      ]);
+
+      final rows = await db.select(db.species).get();
+      expect(rows.single.id, 'legacy'); // same row, not a duplicate
+      expect(rows.single.gbifKey, 5290052);
+      expect(rows.single.wikidataQid, 'Q11575');
+    },
+  );
+
   test('seedBundled inserts species and is idempotent', () async {
     await repo.seedBundled(_seeds);
     await repo.seedBundled(_seeds); // second run must not duplicate

apps/app_seeds/test/domain/species_reference_links_test.dart

@@ -0,0 +1,84 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/domain/species_reference_links.dart';
+
+void main() {
+  test('all identifiers present yields gbif, wikipedia and wikispecies', () {
+    final links = speciesReferenceLinks(
+      scientificName: 'Solanum lycopersicum',
+      gbifKey: 2930137,
+      wikidataQid: 'Q23501',
+      languageCode: 'es',
+    );
+    expect(links.map((l) => l.source), [
+      ReferenceSource.gbif,
+      ReferenceSource.wikipedia,
+      ReferenceSource.wikispecies,
+    ]);
+    expect(links[0].url, 'https://www.gbif.org/species/2930137');
+    expect(
+      links[1].url,
+      'https://www.wikidata.org/wiki/Special:GoToLinkedPage/eswiki/Q23501',
+    );
+    expect(
+      links[2].url,
+      'https://species.wikimedia.org/wiki/Solanum_lycopersicum',
+    );
+  });
+
+  test('wikipedia link is locale-aware', () {
+    String wiki(String lang) => speciesReferenceLinks(
+      scientificName: 'Zea mays',
+      wikidataQid: 'Q11575',
+      languageCode: lang,
+    ).firstWhere((l) => l.source == ReferenceSource.wikipedia).url;
+
+    expect(wiki('en'), contains('/enwiki/Q11575'));
+    expect(wiki('ar'), contains('/arwiki/Q11575'));
+  });
+
+  test('locale region and case are normalised to the bare wiki subtag', () {
+    String wiki(String lang) => speciesReferenceLinks(
+      scientificName: 'Zea mays',
+      wikidataQid: 'Q11575',
+      languageCode: lang,
+    ).firstWhere((l) => l.source == ReferenceSource.wikipedia).url;
+
+    expect(wiki('pt_BR'), contains('/ptwiki/'));
+    expect(wiki('zh-Hans'), contains('/zhwiki/'));
+    expect(wiki('EN'), contains('/enwiki/'));
+    expect(wiki(''), contains('/enwiki/')); // empty locale → English
+  });
+
+  test('a missing identifier simply drops that source', () {
+    final onlyGbif = speciesReferenceLinks(
+      scientificName: '', // no wikispecies without a name
+      gbifKey: 42,
+    );
+    expect(onlyGbif.map((l) => l.source), [ReferenceSource.gbif]);
+
+    final blankQid = speciesReferenceLinks(
+      scientificName: 'Daucus carota',
+      wikidataQid: '  ',
+    );
+    expect(
+      blankQid.map((l) => l.source),
+      isNot(contains(ReferenceSource.wikipedia)),
+    );
+    expect(blankQid.map((l) => l.source), [ReferenceSource.wikispecies]);
+  });
+
+  test('nothing identifiable yields no links', () {
+    expect(speciesReferenceLinks(scientificName: '   '), isEmpty);
+  });
+
+  test('scientific names with spaces and diacritics are URL-safe', () {
+    final link = speciesReferenceLinks(
+      scientificName: 'Allium × proliferum',
+    ).single;
+    expect(link.source, ReferenceSource.wikispecies);
+    expect(
+      link.url,
+      'https://species.wikimedia.org/wiki/Allium_%C3%97_proliferum',
+    );
+  });
+}

apps/app_seeds/test/ui/variety_detail_screen_test.dart

@@ -373,6 +373,56 @@ void main() {
     await disposeTree(tester);
   });
 
+  testWidgets(
+    'a linked species with identifiers shows verified reference links',
+    (tester) async {
+      final repo = newTestRepository(db);
+      final species = newTestSpeciesRepository(db);
+      await species.seedBundled(const [
+        SpeciesSeed(
+          scientificName: 'Solanum lycopersicum',
+          gbifKey: 2930137,
+          wikidataQid: 'Q23501',
+        ),
+      ]);
+      final match = (await species.search('Solanum')).single;
+      final id = await repo.addQuickVariety(label: 'Tomato');
+      await repo.linkSpecies(id, match.id);
+
+      await tester.pumpWidget(
+        wrapDetail(repository: repo, varietyId: id, species: species),
+      );
+      await tester.pumpAndSettle();
+
+      // The "Learn more" section renders one chip per available source.
+      expect(find.text('Learn more'), findsOneWidget);
+      expect(find.byKey(const Key('ref.gbif')), findsOneWidget);
+      expect(find.byKey(const Key('ref.wikipedia')), findsOneWidget);
+      expect(find.byKey(const Key('ref.wikispecies')), findsOneWidget);
+      await disposeTree(tester);
+    },
+  );
+
+  testWidgets('a variety with no species shows no reference section', (
+    tester,
+  ) async {
+    final repo = newTestRepository(db);
+    final id = await repo.addQuickVariety(label: 'Mystery seed');
+
+    await tester.pumpWidget(
+      wrapDetail(
+        repository: repo,
+        varietyId: id,
+        species: newTestSpeciesRepository(db),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    expect(find.text('Learn more'), findsNothing);
+    expect(find.byKey(const Key('ref.gbif')), findsNothing);
+    await disposeTree(tester);
+  });
+
   testWidgets('plant lots show the Plants chip and hide germination', (
     tester,
   ) async {