feat(app): hint isolation distance when sowing a cross-pollinating crop

One passive line in the batch story after a 'sown today' tap — 'this
species crosses, grow it ~400 m from others' — sourced from the bundled
seed-saving guidance (family default + species override). Selfers get
nothing: the trap is recording isolation religiously for beans where it
never mattered. No input fields, no schema change.

apps/app_seeds/lib/i18n/en.i18n.json

@@ -737,7 +737,8 @@
   "ratedMixed": "It did so-so",
   "ratedPoor": "It did poorly",
   "outcomeTitle": "Season note",
-  "outcomeYear": "Season {year}"
+  "outcomeYear": "Season {year}",
+  "isolationHint": "This species crosses with its neighbours — grow it about {meters} m away from others to keep it true"
  },
  "sale": {
   "title": "Sales",