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/i18n/es.i18n.json

@@ -6,7 +6,8 @@
     "save": "Guardar",
     "cancel": "Cancelar",
     "delete": "Eliminar",
-    "edit": "Editar"
+    "edit": "Editar",
+    "type": "Tipo"
   },
   "inventory": {
     "title": "Inventario",
@@ -54,26 +55,38 @@
   "addLot": {
     "title": "Añadir lote",
     "year": "Año de cosecha",
-    "quantity": "Cantidad"
+    "quantity": "¿Cuánta?",
+    "amount": "Cantidad"
   },
-  "quantityKind": {
+  "lotType": {
+    "seed": "Semillas",
+    "plant": "Plantel"
+  },
+  "unit": {
     "aFew": "unas pocas",
     "some": "algunas",
     "plenty": "muchas",
-    "handful": "un puñado",
     "pinch": "una pizca",
-    "jar": "un tarro",
-    "packet": "un sobre",
-    "cob": "una mazorca",
-    "head": "una cabezuela",
-    "pod": "una vaina",
-    "ear": "una espiga",
-    "fruit": "un fruto",
-    "bulb": "un bulbo",
-    "tuber": "un tubérculo",
-    "seedHead": "una cabeza de semillas",
-    "bunch": "un manojo",
-    "grams": "gramos",
-    "count": "unidades"
+    "handful": { "singular": "puñado", "plural": "puñados" },
+    "teaspoon": { "singular": "cucharadita", "plural": "cucharaditas" },
+    "spoon": { "singular": "cuchara", "plural": "cucharas" },
+    "cup": { "singular": "taza", "plural": "tazas" },
+    "jar": { "singular": "bote", "plural": "botes" },
+    "sack": { "singular": "saco", "plural": "sacos" },
+    "packet": { "singular": "sobre", "plural": "sobres" },
+    "cob": { "singular": "mazorca", "plural": "mazorcas" },
+    "pod": { "singular": "vaina", "plural": "vainas" },
+    "ear": { "singular": "espiga", "plural": "espigas" },
+    "head": { "singular": "cabezuela", "plural": "cabezuelas" },
+    "fruit": { "singular": "fruto", "plural": "frutos" },
+    "bulb": { "singular": "bulbo", "plural": "bulbos" },
+    "tuber": { "singular": "tubérculo", "plural": "tubérculos" },
+    "seedHead": { "singular": "cabeza de semillas", "plural": "cabezas de semillas" },
+    "bunch": { "singular": "manojo", "plural": "manojos" },
+    "plant": { "singular": "planta", "plural": "plantas" },
+    "pot": { "singular": "maceta", "plural": "macetas" },
+    "tray": { "singular": "bandeja", "plural": "bandejas" },
+    "grams": { "singular": "gramo", "plural": "gramos" },
+    "count": { "singular": "semilla", "plural": "semillas" }
   }
 }