Admin: gestión de opciones de oro (home_goldprice)

- lib/admin-gold.ts: list/create/delete sobre home_goldprice (id, gold_amount, price).
- API: POST /api/admin/gold, DELETE /api/admin/gold/[id] (403 sin admin).
- UI: /admin/gold con AdminGoldManager (alta ordenada por cantidad + borrado),
  enlace desde el índice del admin.
- i18n es/en (Admin): manageGold, gold, goldAmount, goldPrice, goldUnit, noGold.

Verificado: build OK, /admin/gold 307→login sin sesión, APIs 403 sin admin,
columnas confirmadas en la migración Django.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-next/messages/en.json

@@ -326,7 +326,13 @@
     "voteUrl": "URL",
     "voteImage": "Image URL",
     "votePoints": "VP per vote",
-    "noVotes": "No vote sites."
+    "noVotes": "No vote sites.",
+    "manageGold": "Manage gold options",
+    "gold": "Gold options",
+    "goldAmount": "Gold amount",
+    "goldPrice": "Price (€)",
+    "goldUnit": "gold",
+    "noGold": "No gold options."
   },
   "Vote": {
     "title": "Vote for us",

web-next/messages/es.json

@@ -326,7 +326,13 @@
     "voteUrl": "URL",
     "voteImage": "URL de la imagen",
     "votePoints": "PV por voto",
-    "noVotes": "No hay sitios de voto."
+    "noVotes": "No hay sitios de voto.",
+    "manageGold": "Gestionar opciones de oro",
+    "gold": "Opciones de oro",
+    "goldAmount": "Cantidad de oro",
+    "goldPrice": "Precio (€)",
+    "goldUnit": "oro",
+    "noGold": "No hay opciones de oro."
   },
   "Vote": {
     "title": "Votar por nosotros",