feat(plantare): surface product link + dates; spec the bilateral record

The Plantaré screen stored madeOn/dueBy/varietyId but showed none of them,
so it felt half-built. Surface what's already there (no schema change):

- watchPlantareViews() joins each commitment with its variety label
- tile shows the made-on date, a "Return by {date}" line (amber + "overdue"
  when an open promise is past due, via new seedWarning colour), the variety
  name, and taps through to /variety/:id
- add sheet gains an optional return-by date picker (createPlantare already
  took dueBy)
- variety detail shows a read-only commitments section (hidden when empty,
  no add button — honours the single hand-over door)
- i18n en/es/pt/ast; tests for the join, dueBy round-trip, tile, and section

Also specs the deferred two-sided record in docs/design/plantare-bilateral.md
(Nostr pubkey counterparty, PlantareTransport propose->accept->counter-sign,
deferred key/signature/movement columns, provenance DAG, reputation anchor),
with a faithful transcription of the paper Plantaré v0.4 (BAH-Semillero 2009,
CC-BY-SA). Cross-linked from data-model §2.7 and sharing-model §6.

apps/app_seeds/lib/i18n/pt.i18n.json

@@ -630,7 +630,14 @@
     "statusForgiven": "Saldado",
     "openSection": "Pendentes",
     "settledSection": "Feitos",
-    "removeConfirm": "Remover este compromisso?"
+    "removeConfirm": "Remover este compromisso?",
+    "returnBy": "Devolver até {date}",
+    "overdue": "vencido",
+    "dueByLabel": "Devolver até (opcional)",
+    "dueByHint": "Um lembrete gentil, nunca imposto",
+    "pickDate": "Escolher data",
+    "clearDate": "Limpar data",
+    "sectionTitle": "Compromissos"
   },
   "handover": {
     "title": "Dei ou recebi sementes",