feat(inventory): photo gallery + reactive avatars (+ harvest month/year)

Photos:
- Repository addPhoto/removePhoto; VarietyDetail.photos (list); loads all photos.
- Detail: a 140×140 photo carousel with page dots, delete-current, and add-photo
  (gallery); empty state shows an add-photo button.
- watchInventory now re-emits on attachment + species changes (StreamGroup), so
  a photo added on the detail screen refreshes the inventory avatar immediately
  (fixes avatars not updating).

Also carries the concurrent harvest-date work: lots gain an optional harvest
month (schemaVersion 3 + from2To3 migration, drift_schema_v3 exported), a
month/year harvest picker, and localized month names.

48 tests green (add/remove photos, avatar reactivity, v1→v3 migration); Linux runs.

apps/app_seeds/test/data/variety_detail_test.dart

@@ -1,3 +1,5 @@
+import 'dart:typed_data';
+
 import 'package:async/async.dart';
 import 'package:commons_core/commons_core.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -184,4 +186,30 @@ void main() {
     await repo.removeVernacularName(nameId);
     expect((await repo.watchVariety(id).first)!.vernacularNames, isEmpty);
   });
+
+  test('add and remove photos (multiple, ordered)', () async {
+    final id = await repo.addQuickVariety(label: 'Maize');
+    final p1 = await repo.addPhoto(id, Uint8List.fromList([1, 2, 3]));
+    await repo.addPhoto(id, Uint8List.fromList([4, 5, 6]));
+
+    expect((await repo.watchVariety(id).first)!.photos.length, 2);
+
+    await repo.removePhoto(p1);
+    final photos = (await repo.watchVariety(id).first)!.photos;
+    expect(photos.map((p) => p.bytes.toList()), [
+      [4, 5, 6],
+    ]);
+  });
+
+  test('watchInventory avatar refreshes when a photo is added later', () async {
+    final id = await repo.addQuickVariety(label: 'Maize');
+    final queue = StreamQueue(repo.watchInventory());
+
+    expect((await queue.next).single.photo, isNull);
+
+    await repo.addPhoto(id, Uint8List.fromList([1, 2, 3]));
+    expect((await queue.next).single.photo, isNotNull);
+
+    await queue.cancel();
+  });
 }

apps/app_seeds/test/db/migration_test.dart

@@ -18,16 +18,13 @@ void main() {
     await db.close();
   });
 
-  test(
-    'upgrades v1 → v3 (adds Lot.type, then harvestMonth) and matches the '
-    'fresh schema',
-    () async {
-      final connection = await verifier.startAt(1);
-      final db = AppDatabase(connection);
-      await verifier.migrateAndValidate(db, 3);
-      await db.close();
-    },
-  );
+  test('upgrades v1 → v3 (adds Lot.type, then harvestMonth) and matches the '
+      'fresh schema', () async {
+    final connection = await verifier.startAt(1);
+    final db = AppDatabase(connection);
+    await verifier.migrateAndValidate(db, 3);
+    await db.close();
+  });
 
   test(
     'upgrades v2 → v3 (adds Lot.harvestMonth) and matches the fresh schema',