feat(inventory): external links on the variety detail

Add Wikipedia/forum-style URLs to a variety:
- Repository: addExternalLink/removeExternalLink (soft delete); watchVariety
  loads links and re-emits on external_links changes; ExternalLinkItem model
  (title preferred over URL for display).
- Cubit: addExternalLink/removeExternalLink.
- Detail: a "Links" section with tappable link chips (open via url_launcher,
  http(s):// prepended if missing), delete per chip, and an "Add link" dialog
  (URL + optional title).

Tests: repo add/remove + widget add/remove. 52 green; Linux runs.

apps/app_seeds/lib/data/variety_repository.dart

@@ -126,6 +126,22 @@ class VarietyPhoto extends Equatable {
   List<Object?> get props => [id, bytes];
 }
 
+/// An external URL attached to a variety (Wikipedia, a forum thread…).
+class ExternalLinkItem extends Equatable {
+  const ExternalLinkItem({required this.id, required this.url, this.title});
+
+  final String id;
+  final String url;
+  final String? title;
+
+  /// What to show: the title if present, otherwise the URL.
+  String get display =>
+      (title != null && title!.trim().isNotEmpty) ? title! : url;
+
+  @override
+  List<Object?> get props => [id, url, title];
+}
+
 /// The full detail of one variety (identity + its lots, names and photos).
 class VarietyDetail extends Equatable {
   const VarietyDetail({
@@ -138,6 +154,7 @@ class VarietyDetail extends Equatable {
     this.lots = const [],
     this.vernacularNames = const [],
     this.photos = const [],
+    this.links = const [],
   });
 
   final String id;
@@ -149,6 +166,7 @@ class VarietyDetail extends Equatable {
   final List<VarietyLot> lots;
   final List<VernacularName> vernacularNames;
   final List<VarietyPhoto> photos;
+  final List<ExternalLinkItem> links;
 
   @override
   List<Object?> get props => [
@@ -161,6 +179,7 @@ class VarietyDetail extends Equatable {
     lots,
     vernacularNames,
     photos,
+    links,
   ];
 }
 
@@ -347,6 +366,9 @@ class VarietyRepository {
       (_db.select(
         _db.attachments,
       )..where((a) => a.parentId.equals(id))).watch().map((_) {}),
+      (_db.select(
+        _db.externalLinks,
+      )..where((e) => e.parentId.equals(id))).watch().map((_) {}),
       // Coarse: any germination-test change re-emits (catalog of tests is tiny).
       _db.select(_db.germinationTests).watch().map((_) {}),
     ]);
@@ -412,6 +434,17 @@ class VarietyRepository {
               ..orderBy([(a) => OrderingTerm(expression: a.createdAt)]))
             .get();
 
+    final links =
+        await (_db.select(_db.externalLinks)
+              ..where(
+                (e) =>
+                    e.parentId.equals(id) &
+                    e.parentType.equalsValue(ParentType.variety) &
+                    e.isDeleted.equals(false),
+              )
+              ..orderBy([(e) => OrderingTerm(expression: e.createdAt)]))
+            .get();
+
     return VarietyDetail(
       id: v.id,
       label: v.label,
@@ -434,6 +467,9 @@ class VarietyRepository {
         for (final p in photos)
           if (p.bytes != null) VarietyPhoto(id: p.id, bytes: p.bytes!),
       ],
+      links: links
+          .map((e) => ExternalLinkItem(id: e.id, url: e.url, title: e.title))
+          .toList(),
     );
   }
 
@@ -630,6 +666,45 @@ class VarietyRepository {
     );
   }
 
+  /// Adds an external link (URL, optional title) to a variety. Returns its id.
+  Future<String> addExternalLink(
+    String varietyId,
+    String url, {
+    String? title,
+  }) async {
+    final (created, updated) = _stamp();
+    final id = idGen.newId();
+    await _db
+        .into(_db.externalLinks)
+        .insert(
+          ExternalLinksCompanion.insert(
+            id: id,
+            createdAt: created,
+            updatedAt: updated,
+            lastAuthor: nodeId,
+            parentType: ParentType.variety,
+            parentId: varietyId,
+            url: url,
+            title: Value(title),
+          ),
+        );
+    return id;
+  }
+
+  /// Soft-deletes an external link (tombstone).
+  Future<void> removeExternalLink(String linkId) async {
+    final (_, updated) = _stamp();
+    await (_db.update(
+      _db.externalLinks,
+    )..where((e) => e.id.equals(linkId))).write(
+      ExternalLinksCompanion(
+        isDeleted: const Value(true),
+        updatedAt: Value(updated),
+        lastAuthor: Value(nodeId),
+      ),
+    );
+  }
+
   /// Soft-deletes a variety (tombstone); it disappears from the inventory but
   /// the row survives for correct CRDT merges later.
   Future<void> softDeleteVariety(String id) async {

apps/app_seeds/lib/i18n/en.i18n.json

@@ -45,6 +45,10 @@
     "noLots": "No lots yet.",
     "names": "Also known as",
     "addName": "Add name",
+    "links": "Links",
+    "addLink": "Add link",
+    "linkUrl": "URL",
+    "linkTitle": "Title (optional)",
     "notes": "Notes",
     "addLot": "Add lot",
     "editLot": "Edit lot",

apps/app_seeds/lib/i18n/es.i18n.json

@@ -45,6 +45,10 @@
     "noLots": "Aún no hay lotes.",
     "names": "También conocida como",
     "addName": "Añadir nombre",
+    "links": "Enlaces",
+    "addLink": "Añadir enlace",
+    "linkUrl": "URL",
+    "linkTitle": "Título (opcional)",
     "notes": "Notas",
     "addLot": "Añadir lote",
     "editLot": "Editar lote",

apps/app_seeds/lib/i18n/strings.g.dart

@@ -4,9 +4,9 @@
 /// To regenerate, run: `dart run slang`
 ///
 /// Locales: 2
-/// Strings: 236 (118 per locale)
+/// Strings: 244 (122 per locale)
 ///
-/// Built on 2026-07-08 at 10:18 UTC
+/// Built on 2026-07-08 at 10:27 UTC
 
 // coverage:ignore-file
 // ignore_for_file: type=lint, unused_import

apps/app_seeds/lib/i18n/strings_en.g.dart

@@ -216,6 +216,18 @@ class Translations$detail$en {
 	/// en: 'Add name'
 	String get addName => 'Add name';
 
+	/// en: 'Links'
+	String get links => 'Links';
+
+	/// en: 'Add link'
+	String get addLink => 'Add link';
+
+	/// en: 'URL'
+	String get linkUrl => 'URL';
+
+	/// en: 'Title (optional)'
+	String get linkTitle => 'Title (optional)';
+
 	/// en: 'Notes'
 	String get notes => 'Notes';
 
@@ -757,6 +769,10 @@ extension on Translations {
 			'detail.noLots' => 'No lots yet.',
 			'detail.names' => 'Also known as',
 			'detail.addName' => 'Add name',
+			'detail.links' => 'Links',
+			'detail.addLink' => 'Add link',
+			'detail.linkUrl' => 'URL',
+			'detail.linkTitle' => 'Title (optional)',
 			'detail.notes' => 'Notes',
 			'detail.addLot' => 'Add lot',
 			'detail.editLot' => 'Edit lot',

apps/app_seeds/lib/i18n/strings_es.g.dart

@@ -148,6 +148,10 @@ class _Translations$detail$es extends Translations$detail$en {
 	@override String get noLots => 'Aún no hay lotes.';
 	@override String get names => 'También conocida como';
 	@override String get addName => 'Añadir nombre';
+	@override String get links => 'Enlaces';
+	@override String get addLink => 'Añadir enlace';
+	@override String get linkUrl => 'URL';
+	@override String get linkTitle => 'Título (opcional)';
 	@override String get notes => 'Notas';
 	@override String get addLot => 'Añadir lote';
 	@override String get editLot => 'Editar lote';
@@ -542,6 +546,10 @@ extension on TranslationsEs {
 			'detail.noLots' => 'Aún no hay lotes.',
 			'detail.names' => 'También conocida como',
 			'detail.addName' => 'Añadir nombre',
+			'detail.links' => 'Enlaces',
+			'detail.addLink' => 'Añadir enlace',
+			'detail.linkUrl' => 'URL',
+			'detail.linkTitle' => 'Título (opcional)',
 			'detail.notes' => 'Notas',
 			'detail.addLot' => 'Añadir lote',
 			'detail.editLot' => 'Editar lote',

apps/app_seeds/lib/state/variety_detail_cubit.dart

@@ -92,6 +92,12 @@ class VarietyDetailCubit extends Cubit<VarietyDetailState> {
   Future<void> removePhoto(String attachmentId) =>
       _repo.removePhoto(attachmentId);
 
+  Future<void> addExternalLink(String url, {String? title}) =>
+      _repo.addExternalLink(varietyId, url, title: title);
+
+  Future<void> removeExternalLink(String linkId) =>
+      _repo.removeExternalLink(linkId);
+
   Future<void> linkSpecies(String speciesId) =>
       _repo.linkSpecies(varietyId, speciesId);
 

apps/app_seeds/lib/ui/variety_detail_screen.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
 import 'package:image_picker/image_picker.dart';
+import 'package:url_launcher/url_launcher.dart';
 
 import '../data/species_repository.dart';
 import '../data/variety_repository.dart';
@@ -106,6 +107,30 @@ class _DetailView extends StatelessWidget {
             Text(detail.notes!),
           ],
           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),
+              ),
+            ],
+          ),
+          const SizedBox(height: 16),
           Row(
             mainAxisAlignment: MainAxisAlignment.spaceBetween,
             children: [
@@ -648,6 +673,66 @@ Future<void> _showAddNameDialog(
   );
 }
 
+Future<void> _openUrl(String url) async {
+  final normalized = url.contains('://') ? url : 'https://$url';
+  final uri = Uri.tryParse(normalized);
+  if (uri != null) {
+    await launchUrl(uri, mode: LaunchMode.externalApplication);
+  }
+}
+
+Future<void> _showAddLinkDialog(
+  BuildContext context,
+  VarietyDetailCubit cubit,
+) {
+  final t = context.t;
+  final urlController = TextEditingController();
+  final titleController = TextEditingController();
+  void submit(BuildContext dialogContext) {
+    final url = urlController.text.trim();
+    if (url.isNotEmpty) {
+      cubit.addExternalLink(url, title: _nullIfBlank(titleController.text));
+    }
+    Navigator.of(dialogContext).pop();
+  }
+
+  return showDialog<void>(
+    context: context,
+    builder: (dialogContext) => AlertDialog(
+      title: Text(t.detail.addLink),
+      content: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          TextField(
+            key: const Key('link.url'),
+            controller: urlController,
+            autofocus: true,
+            keyboardType: TextInputType.url,
+            decoration: InputDecoration(labelText: t.detail.linkUrl),
+          ),
+          const SizedBox(height: 8),
+          TextField(
+            key: const Key('link.title'),
+            controller: titleController,
+            decoration: InputDecoration(labelText: t.detail.linkTitle),
+          ),
+        ],
+      ),
+      actions: [
+        TextButton(
+          onPressed: () => Navigator.of(dialogContext).pop(),
+          child: Text(t.common.cancel),
+        ),
+        FilledButton(
+          key: const Key('link.save'),
+          onPressed: () => submit(dialogContext),
+          child: Text(t.common.save),
+        ),
+      ],
+    ),
+  );
+}
+
 String? _nullIfBlank(String value) {
   final trimmed = value.trim();
   return trimmed.isEmpty ? null : trimmed;

apps/app_seeds/linux/flutter/generated_plugin_registrant.cc

@@ -9,6 +9,7 @@
 #include <file_selector_linux/file_selector_plugin.h>
 #include <flutter_secure_storage_linux/flutter_secure_storage_linux_plugin.h>
 #include <sqlcipher_flutter_libs/sqlite3_flutter_libs_plugin.h>
+#include <url_launcher_linux/url_launcher_plugin.h>
 
 void fl_register_plugins(FlPluginRegistry* registry) {
   g_autoptr(FlPluginRegistrar) file_selector_linux_registrar =
@@ -20,4 +21,7 @@ void fl_register_plugins(FlPluginRegistry* registry) {
   g_autoptr(FlPluginRegistrar) sqlcipher_flutter_libs_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "Sqlite3FlutterLibsPlugin");
   sqlite3_flutter_libs_plugin_register_with_registrar(sqlcipher_flutter_libs_registrar);
+  g_autoptr(FlPluginRegistrar) url_launcher_linux_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "UrlLauncherPlugin");
+  url_launcher_plugin_register_with_registrar(url_launcher_linux_registrar);
 }

apps/app_seeds/linux/flutter/generated_plugins.cmake

@@ -6,6 +6,7 @@ list(APPEND FLUTTER_PLUGIN_LIST
   file_selector_linux
   flutter_secure_storage_linux
   sqlcipher_flutter_libs
+  url_launcher_linux
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST

apps/app_seeds/pubspec.yaml

@@ -49,6 +49,7 @@ dependencies:
 
   cupertino_icons: ^1.0.8
   material_symbols_icons: ^4.2951.0
+  url_launcher: ^6.3.2
 
 dev_dependencies:
   flutter_test:

apps/app_seeds/test/data/variety_detail_test.dart

@@ -212,4 +212,20 @@ void main() {
 
     await queue.cancel();
   });
+
+  test('add and remove external links', () async {
+    final id = await repo.addQuickVariety(label: 'Maize');
+    final linkId = await repo.addExternalLink(
+      id,
+      'https://en.wikipedia.org/wiki/Maize',
+      title: 'Wikipedia',
+    );
+
+    final detail = await repo.watchVariety(id).first;
+    expect(detail!.links.single.url, 'https://en.wikipedia.org/wiki/Maize');
+    expect(detail.links.single.display, 'Wikipedia'); // title preferred
+
+    await repo.removeExternalLink(linkId);
+    expect((await repo.watchVariety(id).first)!.links, isEmpty);
+  });
 }

apps/app_seeds/test/ui/variety_detail_screen_test.dart

@@ -329,4 +329,33 @@ void main() {
     expect(find.text('Maíz'), findsNothing);
     await disposeTree(tester);
   });
+
+  testWidgets('adding and removing an external link', (tester) async {
+    final repo = newTestRepository(db);
+    final id = await repo.addQuickVariety(label: 'Maize');
+
+    await tester.pumpWidget(
+      wrapDetail(
+        repository: repo,
+        varietyId: id,
+        species: newTestSpeciesRepository(db),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    await tester.tap(find.byKey(const Key('link.add')));
+    await tester.pumpAndSettle();
+    await tester.enterText(find.byKey(const Key('link.url')), 'wikipedia.org');
+    await tester.enterText(find.byKey(const Key('link.title')), 'Wiki');
+    await tester.tap(find.byKey(const Key('link.save')));
+    await tester.pumpAndSettle();
+
+    expect(find.text('Wiki'), findsOneWidget);
+
+    await tester.tap(find.byIcon(Icons.close)); // the link chip's delete icon
+    await tester.pumpAndSettle();
+
+    expect(find.text('Wiki'), findsNothing);
+    await disposeTree(tester);
+  });
 }

pubspec.lock

@@ -1041,6 +1041,70 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.4.0"
+  url_launcher:
+    dependency: transitive
+    description:
+      name: url_launcher
+      sha256: f6a7e5c4835bb4e3026a04793a4199ca2d14c739ec378fdfe23fc8075d0439f8
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.3.2"
+  url_launcher_android:
+    dependency: transitive
+    description:
+      name: url_launcher_android
+      sha256: "17bc677f0b301615530dd1d67e0a9828cafa2d0b6b6eae4cd3679b7eac4a273c"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.3.30"
+  url_launcher_ios:
+    dependency: transitive
+    description:
+      name: url_launcher_ios
+      sha256: "580fe5dfb51671ae38191d316e027f6b76272b026370708c2d898799750a02b0"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.4.1"
+  url_launcher_linux:
+    dependency: transitive
+    description:
+      name: url_launcher_linux
+      sha256: d5e14138b3bc193a0f63c10a53c94b91d399df0512b1f29b94a043db7482384a
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.2.2"
+  url_launcher_macos:
+    dependency: transitive
+    description:
+      name: url_launcher_macos
+      sha256: "368adf46f71ad3c21b8f06614adb38346f193f3a59ba8fe9a2fd74133070ba18"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.2.5"
+  url_launcher_platform_interface:
+    dependency: transitive
+    description:
+      name: url_launcher_platform_interface
+      sha256: "552f8a1e663569be95a8190206a38187b531910283c3e982193e4f2733f01029"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.3.2"
+  url_launcher_web:
+    dependency: transitive
+    description:
+      name: url_launcher_web
+      sha256: "85c81589622fbc87c1c683aaea164d3604a7777495a79d91e39ffcdec39ddb34"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.4.3"
+  url_launcher_windows:
+    dependency: transitive
+    description:
+      name: url_launcher_windows
+      sha256: "712c70ab1b99744ff066053cbe3e80c73332b38d46e5e945c98689b2e66fc15f"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.5"
   uuid:
     dependency: transitive
     description: