feat(handover): one hand-over sheet replaces the separate sale/plantare doors

'Seeds changed hands' is now the single entry point on the variety
detail (and per lot row): direction (gave/received), one-tap 'all of it'
(default — the whole-plant/shrub case), optional partial quantity,
counterparty, and reveal-on-tap money and return-promise sections that
spawn the Sale/Plantare rows through recordHandover in one save.

Zero-lot varieties still work (ledger rows only); several lots get a
chip picker. The Sales/Plantares screens keep their own add buttons for
off-app records — the sheets stay, demoted to secondary.

i18n handover block in en/es/pt/ast; widget tests for the flow.

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

@@ -621,6 +621,19 @@
     "settledSection": "Hechos",
     "removeConfirm": "¿Quitar este compromiso?"
   },
+  "handover": {
+    "title": "Di o recibí semillas",
+    "help": "Un regalo, un trueque o una venta: apúntalo, con promesa de devolver semilla o sin ella.",
+    "iGave": "Di semillas",
+    "iReceived": "Recibí semillas",
+    "whichLot": "¿De qué lote?",
+    "howMuch": "¿Cuánto?",
+    "allOfIt": "Todo",
+    "partOfIt": "Una parte",
+    "paymentChip": "Hubo dinero por medio",
+    "promiseGave": "Me devolverán semilla",
+    "promiseReceived": "Devolveré semilla"
+  },
   "sale": {
     "title": "Ventas",
     "help": "Registra semilla vendida o comprada — dinero, Ğ1 o cualquier moneda. Un modelo aparte del regalo y del Plantare. Nunca se cobra comisión por las semillas.",