feat(seed-saving): source attribution + advisory note

Record where the guidance comes from (copyright/attribution) and make
clear it is general, not local gospel — kept light:
- seed_saving.json gains a top-level sources list (Seed to Seed / Seed
  Savers Exchange / Organic Seed Alliance); parsed into
  SeedSavingData.sources, exposed via SeedSavingCatalog.sources.
- The detail section shows a small muted footer: an italic 'advisory —
  adapt to your climate' line plus a 'Source: …' credit.
- i18n seedSaving.advisory + sourcePrefix (en/es/pt/ast).
- Tests: asset carries sources; the section renders advisory + credit.

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

@@ -23,7 +23,9 @@
     "difficulty": "Dificuldade",
     "diffEasy": "Fácil",
     "diffMedium": "Média",
-    "diffHard": "Difícil"
+    "diffHard": "Difícil",
+    "advisory": "Orientativo — adapte-o ao seu clima e variedade.",
+    "sourcePrefix": "Fonte"
   },
   "calendar": {
     "title": "Este mês",