feat(inventory): informal quantity scale (number + unit) + seed/plant lots

Rework quantities the way seeds are actually described — a number of an informal
unit — and let a lot hold seeds or plants (plantel).

Quantity model (commons_core):
- Quantity is now { kind, count?, label } — "3 cobs", "2 packets", "a few".
  Count is optional; uncountable vibes (a few, some, pinch) carry no number.
- QuantityKind reorganised into an ascending scale: vibes → containers
  (teaspoon/spoon/cup/jar/sack) → seed & fruit forms → plant units, each tagged
  countable/not. Stored by name; count reuses the existing numeric column.

Lot type (schema v2):
- Lots gain a `type` (seed | plant); germination stays meaningful for seeds.
  schemaVersion 2 with a from1To2 migration (adds the column), drift_schema_v2
  exported, migration test covers v1→v2.

UI:
- New QuantityPicker: a horizontal scale of large seed-glyph icons + a number
  stepper (shown only for countable units), plus a seed/plant SegmentedButton.
  Used in quick-add and add-lot. Lot lines render "3 cobs" / "a few".
- i18n: unit singular/plural (ES/EN, Weblate-friendly), lot-type labels.

Build: slang moved to its CLI (disabled in build_runner to avoid a multi-file
collision); CI runs `dart run slang` before build_runner. 38 tests green,
Linux migrates the existing v1 DB and runs.

apps/app_seeds/lib/data/variety_repository.dart

@@ -63,6 +63,7 @@ class GerminationEntry extends Equatable {
 class VarietyLot extends Equatable {
   const VarietyLot({
     required this.id,
+    this.type = LotType.seed,
     this.harvestYear,
     this.quantity,
     this.storageLocation,
@@ -70,6 +71,7 @@ class VarietyLot extends Equatable {
   });
 
   final String id;
+  final LotType type;
   final int? harvestYear;
   final Quantity? quantity;
   final String? storageLocation;
@@ -82,6 +84,7 @@ class VarietyLot extends Equatable {
   @override
   List<Object?> get props => [
     id,
+    type,
     harvestYear,
     quantity,
     storageLocation,
@@ -216,6 +219,7 @@ class VarietyRepository {
   Future<String> addQuickVariety({
     required String label,
     String? category,
+    LotType lotType = LotType.seed,
     Quantity? quantity,
     Uint8List? photoBytes,
   }) async {
@@ -246,8 +250,9 @@ class VarietyRepository {
                 createdAt: created,
                 updatedAt: updated,
                 lastAuthor: nodeId,
+                type: Value(lotType),
                 quantityKind: Value(quantity.kind.name),
-                quantityPrecise: Value(quantity.precise),
+                quantityPrecise: Value(quantity.count?.toDouble()),
                 quantityLabel: Value(quantity.label),
               ),
             );
@@ -423,6 +428,7 @@ class VarietyRepository {
   /// Adds a lot (a held batch) to a variety. Returns the new lot id.
   Future<String> addLot({
     required String varietyId,
+    LotType type = LotType.seed,
     int? harvestYear,
     Quantity? quantity,
     String? storageLocation,
@@ -438,9 +444,10 @@ class VarietyRepository {
             createdAt: created,
             updatedAt: updated,
             lastAuthor: nodeId,
+            type: Value(type),
             harvestYear: Value(harvestYear),
             quantityKind: Value(quantity?.kind.name),
-            quantityPrecise: Value(quantity?.precise),
+            quantityPrecise: Value(quantity?.count?.toDouble()),
             quantityLabel: Value(quantity?.label),
             storageLocation: Value(storageLocation),
           ),
@@ -496,13 +503,14 @@ class VarietyRepository {
         l.quantityLabel != null;
     return VarietyLot(
       id: l.id,
+      type: l.type,
       harvestYear: l.harvestYear,
       storageLocation: l.storageLocation,
       germinationTests: germinationTests,
       quantity: hasQuantity
           ? Quantity(
               kind: _parseKind(l.quantityKind),
-              precise: l.quantityPrecise,
+              count: l.quantityPrecise,
               label: l.quantityLabel,
             )
           : null,