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/ui/plantares_screen.dart

@@ -1,8 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:go_router/go_router.dart';
 
 import '../data/variety_repository.dart';
-import '../db/database.dart';
 import '../db/enums.dart';
 import '../i18n/strings.g.dart';
 import 'plantare_sheet.dart';
@@ -26,8 +26,8 @@ class PlantaresScreen extends StatelessWidget {
         icon: const Icon(Icons.add),
         label: Text(t.plantare.add),
       ),
-      body: StreamBuilder<List<Plantare>>(
-        stream: repo.watchPlantares(),
+      body: StreamBuilder<List<PlantareView>>(
+        stream: repo.watchPlantareViews(),
         builder: (context, snapshot) {
           final all = snapshot.data;
           if (all == null) {
@@ -45,15 +45,17 @@ class PlantaresScreen extends StatelessWidget {
               ),
             );
           }
-          final open = all.where((p) => p.status == PlantareStatus.open);
-          final settled = all.where((p) => p.status != PlantareStatus.open);
+          final open =
+              all.where((v) => v.plantare.status == PlantareStatus.open);
+          final settled =
+              all.where((v) => v.plantare.status != PlantareStatus.open);
           return ListView(
             padding: const EdgeInsets.only(bottom: 88),
             children: [
               if (open.isNotEmpty) _SectionHeader(t.plantare.openSection),
-              for (final p in open) _PlantareTile(p, repo),
+              for (final v in open) _PlantareTile(v, repo),
               if (settled.isNotEmpty) _SectionHeader(t.plantare.settledSection),
-              for (final p in settled) _PlantareTile(p, repo),
+              for (final v in settled) _PlantareTile(v, repo),
             ],
           );
         },
@@ -82,30 +84,54 @@ class _SectionHeader extends StatelessWidget {
 }
 
 /// One commitment row. An open one shows a big "mark returned"; a settled one
-/// reads muted. The overflow menu carries the rest (let go / reopen / remove).
+/// reads muted. It names the seed and (when linked) taps through to its detail,
+/// shows when it was made and — for a promise with a return-by date — whether
+/// it's still ahead or overdue. The overflow menu carries the rest (let go /
+/// reopen / remove).
 class _PlantareTile extends StatelessWidget {
-  const _PlantareTile(this.p, this.repo);
+  const _PlantareTile(this.view, this.repo);
 
-  final Plantare p;
+  final PlantareView view;
   final VarietyRepository repo;
 
   @override
   Widget build(BuildContext context) {
     final t = context.t;
+    final p = view.plantare;
+    final varietyLabel = view.varietyLabel;
     final done = p.status != PlantareStatus.open;
     final iReturn = p.direction == PlantareDirection.iReturn;
     final title = (p.owedDescription?.trim().isNotEmpty ?? false)
         ? p.owedDescription!.trim()
         : (iReturn ? t.plantare.iReturn : t.plantare.owedToMe);
+    final locals = MaterialLocalizations.of(context);
+    final made = locals
+        .formatShortDate(DateTime.fromMillisecondsSinceEpoch(p.madeOn));
     final subtitleParts = <String>[
       iReturn ? t.plantare.iReturn : t.plantare.owedToMe,
+      ?varietyLabel,
       if (p.counterparty?.trim().isNotEmpty ?? false) p.counterparty!.trim(),
+      made,
       if (done)
         p.status == PlantareStatus.returned
             ? t.plantare.statusReturned
             : t.plantare.statusForgiven,
     ];
+    // A return-by date is a gentle nudge, not a debt: only an open, past-due
+    // promise reads as overdue.
+    final overdue = !done &&
+        p.dueBy != null &&
+        p.dueBy! < DateTime.now().millisecondsSinceEpoch;
+    final returnBy = p.dueBy == null
+        ? null
+        : t.plantare.returnBy(
+            date: locals.formatShortDate(
+              DateTime.fromMillisecondsSinceEpoch(p.dueBy!),
+            ),
+          );
+    final linkedId = varietyLabel == null ? null : p.varietyId;
     return ListTile(
+      onTap: linkedId == null ? null : () => context.push('/variety/$linkedId'),
       leading: Icon(
         iReturn ? Icons.volunteer_activism_outlined : Icons.eco_outlined,
         color: done ? seedMuted : seedGreen,
@@ -117,8 +143,21 @@ class _PlantareTile extends StatelessWidget {
           color: done ? seedMuted : seedOnSurface,
         ),
       ),
-      subtitle: Text(subtitleParts.join(' · '),
-          maxLines: 2, overflow: TextOverflow.ellipsis),
+      subtitle: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: [
+          Text(subtitleParts.join(' · '),
+              maxLines: 2, overflow: TextOverflow.ellipsis),
+          if (returnBy != null)
+            Text(
+              overdue ? '$returnBy · ${t.plantare.overdue}' : returnBy,
+              style: TextStyle(
+                color: overdue ? seedWarning : seedMuted,
+                fontWeight: overdue ? FontWeight.w600 : null,
+              ),
+            ),
+        ],
+      ),
       trailing: Row(
         mainAxisSize: MainAxisSize.min,
         children: [