feat(inventory): editable vernacular (common) names

The "also known as" names were read-only; now they can be added and removed:
- Repository: addVernacularName + removeVernacularName (soft delete);
  VarietyDetail.vernacularNames carries ids (new VernacularName model).
- Cubit: addVernacularName / removeVernacularName.
- Detail: deletable name chips + an "Add name" chip opening a small dialog;
  the section is always visible so names can be added when empty.

Tests: repo add/remove + widget add/remove. 44 green.

apps/app_seeds/lib/data/variety_repository.dart

@@ -92,6 +92,24 @@ class VarietyLot extends Equatable {
   ];
 }
 
+/// One vernacular (common) name of a variety.
+class VernacularName extends Equatable {
+  const VernacularName({
+    required this.id,
+    required this.name,
+    this.language,
+    this.region,
+  });
+
+  final String id;
+  final String name;
+  final String? language;
+  final String? region;
+
+  @override
+  List<Object?> get props => [id, name, language, region];
+}
+
 /// The full detail of one variety (identity + its lots, names and first photo).
 class VarietyDetail extends Equatable {
   const VarietyDetail({
@@ -113,7 +131,7 @@ class VarietyDetail extends Equatable {
   final String? speciesId;
   final String? scientificName;
   final List<VarietyLot> lots;
-  final List<String> vernacularNames;
+  final List<VernacularName> vernacularNames;
   final Uint8List? photo;
 
   @override
@@ -373,7 +391,16 @@ class VarietyRepository {
       speciesId: v.speciesId,
       scientificName: scientificName,
       lots: lots.map((l) => _toLot(l, testsByLot[l.id] ?? const [])).toList(),
-      vernacularNames: names.map((n) => n.name).toList(),
+      vernacularNames: names
+          .map(
+            (n) => VernacularName(
+              id: n.id,
+              name: n.name,
+              language: n.language,
+              region: n.region,
+            ),
+          )
+          .toList(),
       photo: photos.isEmpty ? null : photos.first.bytes,
     );
   }
@@ -491,6 +518,46 @@ class VarietyRepository {
     );
   }
 
+  /// Adds a vernacular (common) name to a variety. Returns the new row id.
+  Future<String> addVernacularName(
+    String varietyId,
+    String name, {
+    String? language,
+    String? region,
+  }) async {
+    final (created, updated) = _stamp();
+    final id = idGen.newId();
+    await _db
+        .into(_db.varietyVernacularNames)
+        .insert(
+          VarietyVernacularNamesCompanion.insert(
+            id: id,
+            varietyId: varietyId,
+            name: name,
+            createdAt: created,
+            updatedAt: updated,
+            lastAuthor: nodeId,
+            language: Value(language),
+            region: Value(region),
+          ),
+        );
+    return id;
+  }
+
+  /// Soft-deletes a vernacular name (tombstone).
+  Future<void> removeVernacularName(String nameId) async {
+    final (_, updated) = _stamp();
+    await (_db.update(
+      _db.varietyVernacularNames,
+    )..where((n) => n.id.equals(nameId))).write(
+      VarietyVernacularNamesCompanion(
+        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 {