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/domain/species_reference_links.dart

@@ -0,0 +1,90 @@
+/// A verified external reference for a species, built deterministically from the
+/// bundled catalog's identifiers — never hand-entered. These are read-only
+/// "learn more" pointers, distinct from the links a grower adds by hand.
+enum ReferenceSource { gbif, wikipedia, wikispecies }
+
+/// One reference pointer: which source it is (for the label/icon) and the URL.
+class ReferenceLink {
+  const ReferenceLink({required this.source, required this.url});
+
+  final ReferenceSource source;
+  final String url;
+
+  @override
+  bool operator ==(Object other) =>
+      other is ReferenceLink && other.source == source && other.url == url;
+
+  @override
+  int get hashCode => Object.hash(source, url);
+
+  @override
+  String toString() => 'ReferenceLink($source, $url)';
+}
+
+/// Builds the verified reference links for a species from its bundled
+/// identifiers. Deterministic and offline — no titles are bundled and no
+/// network call is made; each URL is derived from a stable identifier:
+///
+/// * **GBIF** — the taxon page for the backbone [gbifKey].
+/// * **Wikipedia** — locale-aware via Wikidata's `Special:GoToLinkedPage`
+///   redirect, so we need only the [wikidataQid] and the user's [languageCode]:
+///   the redirect resolves to the article in that language, falling back to the
+///   Wikidata item when the language has no article. Works under RTL locales.
+/// * **Wikispecies** — the canonical article keyed by [scientificName].
+///
+/// A source is only included when its required identifier is present, so a
+/// species missing (say) a GBIF key simply yields fewer links.
+List<ReferenceLink> speciesReferenceLinks({
+  required String scientificName,
+  int? gbifKey,
+  String? wikidataQid,
+  String languageCode = 'en',
+}) {
+  final links = <ReferenceLink>[];
+
+  if (gbifKey != null) {
+    links.add(
+      ReferenceLink(
+        source: ReferenceSource.gbif,
+        url: 'https://www.gbif.org/species/$gbifKey',
+      ),
+    );
+  }
+
+  final qid = wikidataQid?.trim();
+  if (qid != null && qid.isNotEmpty) {
+    final lang = _wikiLang(languageCode);
+    links.add(
+      ReferenceLink(
+        source: ReferenceSource.wikipedia,
+        url:
+            'https://www.wikidata.org/wiki/Special:GoToLinkedPage/${lang}wiki/$qid',
+      ),
+    );
+  }
+
+  final title = scientificName.trim();
+  if (title.isNotEmpty) {
+    links.add(
+      ReferenceLink(
+        source: ReferenceSource.wikispecies,
+        url: 'https://species.wikimedia.org/wiki/${_wikiTitle(title)}',
+      ),
+    );
+  }
+
+  return links;
+}
+
+/// The bare Wikipedia language subtag: drops any region (`pt_BR` → `pt`) and
+/// falls back to English for an empty/blank locale.
+String _wikiLang(String languageCode) {
+  final base = languageCode.split(RegExp('[-_]')).first.trim().toLowerCase();
+  return base.isEmpty ? 'en' : base;
+}
+
+/// A MediaWiki page title: spaces become underscores, then non-ASCII is
+/// percent-encoded (scientific names are Latin, but stay safe for hybrids and
+/// diacritics). `_` is left intact by [Uri.encodeFull].
+String _wikiTitle(String scientificName) =>
+    Uri.encodeFull(scientificName.replaceAll(' ', '_'));