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/lib/ui/variety_detail_screen.dart

@@ -10,6 +10,7 @@ import '../data/variety_repository.dart';
 import '../db/enums.dart';
 import '../domain/crop_calendar.dart';
 import '../domain/seed_viability.dart';
+import '../domain/species_reference_links.dart';
 import '../i18n/strings.g.dart';
 import '../state/variety_detail_cubit.dart';
 import 'harvest_date_picker.dart';
@@ -116,29 +117,54 @@ class _DetailView extends StatelessWidget {
             _SectionTitle(t.cropCalendar.title),
             _CropCalendarView(detail: detail),
           ],
-          const SizedBox(height: 16),
-          _SectionTitle(t.detail.links),
-          Wrap(
-            spacing: 8,
-            runSpacing: 4,
-            crossAxisAlignment: WrapCrossAlignment.center,
-            children: [
-              for (final link in detail.links)
-                InputChip(
-                  key: Key('link.${link.id}'),
-                  avatar: const Icon(Icons.link, size: 18),
-                  label: Text(link.display),
-                  deleteIcon: const Icon(Icons.close, size: 18),
-                  onDeleted: () => cubit.removeExternalLink(link.id),
-                  onPressed: () => _openUrl(link.url),
-                ),
-              ActionChip(
-                key: const Key('link.add'),
-                avatar: const Icon(Icons.add, size: 18),
-                label: Text(t.detail.addLink),
-                onPressed: () => _showAddLinkDialog(context, cubit),
-              ),
-            ],
+          if (_referenceLinks(context, detail) case final references
+              when references.isNotEmpty) ...[
+            const SizedBox(height: 16),
+            _SectionTitle(t.detail.reference),
+            Wrap(
+              spacing: 8,
+              runSpacing: 4,
+              children: [
+                for (final ref in references)
+                  ActionChip(
+                    key: Key('ref.${ref.source.name}'),
+                    avatar: const Icon(Icons.open_in_new, size: 18),
+                    label: Text(_referenceLabel(t, ref.source)),
+                    onPressed: () => _openUrl(ref.url),
+                  ),
+              ],
+            ),
+          ],
+          // The grower's own links: a rarer power move, so kept subtle — the
+          // section only appears once there are links, and adding one lives
+          // behind a low-emphasis button rather than a prominent chip.
+          if (detail.links.isNotEmpty) ...[
+            const SizedBox(height: 16),
+            _SectionTitle(t.detail.links),
+            Wrap(
+              spacing: 8,
+              runSpacing: 4,
+              children: [
+                for (final link in detail.links)
+                  InputChip(
+                    key: Key('link.${link.id}'),
+                    avatar: const Icon(Icons.link, size: 18),
+                    label: Text(link.display),
+                    deleteIcon: const Icon(Icons.close, size: 18),
+                    onDeleted: () => cubit.removeExternalLink(link.id),
+                    onPressed: () => _openUrl(link.url),
+                  ),
+              ],
+            ),
+          ],
+          Align(
+            alignment: AlignmentDirectional.centerStart,
+            child: TextButton.icon(
+              key: const Key('link.add'),
+              onPressed: () => _showAddLinkDialog(context, cubit),
+              icon: const Icon(Icons.add_link, size: 18),
+              label: Text(t.detail.addLink),
+            ),
           ),
           const SizedBox(height: 16),
           Row(
@@ -1497,6 +1523,30 @@ Future<void> _showAddNameDialog(
   );
 }
 
+/// Verified reference links for the variety's linked species, localized to the
+/// UI language (drives the locale-aware Wikipedia link). Empty when no species
+/// is linked or the catalog entry carries no identifiers.
+List<ReferenceLink> _referenceLinks(
+  BuildContext context,
+  VarietyDetail detail,
+) {
+  final name = detail.scientificName;
+  if (name == null) return const [];
+  return speciesReferenceLinks(
+    scientificName: name,
+    gbifKey: detail.gbifKey,
+    wikidataQid: detail.wikidataQid,
+    languageCode: Localizations.localeOf(context).languageCode,
+  );
+}
+
+String _referenceLabel(Translations t, ReferenceSource source) =>
+    switch (source) {
+      ReferenceSource.gbif => t.detail.refGbif,
+      ReferenceSource.wikipedia => t.detail.refWikipedia,
+      ReferenceSource.wikispecies => t.detail.refWikispecies,
+    };
+
 Future<void> _openUrl(String url) async {
   final normalized = url.contains('://') ? url : 'https://$url';
   final uri = Uri.tryParse(normalized);