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/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',
+    );
+  });
+}