i18n(chat): translate the Chat UI strings into all 8 languages

Add the 15 HushChat UI strings (nav label, locked/empty/select/waiting hints,
composer + new-conversation dialog, You / contact request / not-sent tags) to
res/lang/{de,es,fr,ja,ko,pt,ru,zh}.json. Previously they fell back to English.

Added directly to the JSON files (935 -> 950 keys, additive only): the
scripts/gen_<lang>.py generators are stale — they emit ~285 fewer keys than the
committed JSONs, so regenerating from them would silently drop translations.
(Pre-existing issue; noted for follow-up. The generators are left untouched.)

Rebuilt the usage-based CJK subset font (res/fonts/NotoSansCJK-Subset.ttf) from
the full JSONs so the new chat glyphs (聊天 / 对话 / 会話 / 답장, etc.) render —
verified every CJK code point in the full JSONs is covered (no glyph regression).

Verified: Linux + Windows build (embedded lang headers regenerated via xxd, font
re-embedded via INCBIN), hygiene clean; per-file diff is additive (15 keys, 0
deletions).

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

res/lang/es.json

@@ -110,6 +110,21 @@
     "bootstrap_warning": "Los datos de bloques existentes (blocks, chainstate, notarizations) se eliminarán y reemplazarán. Su wallet.dat NO será modificado ni eliminado.",
     "cancel": "Cancelar",
     "characters": "caracteres",
+    "chat": "Chat",
+    "chat_cancel": "Cancelar",
+    "chat_contact_request": "solicitud de contacto",
+    "chat_empty_hint": "Aún no hay conversaciones. Los mensajes que recibas aparecerán aquí.",
+    "chat_locked_hint": "Desbloquea tu monedero para cargar tus chats.",
+    "chat_new_button": "Nueva conversación",
+    "chat_new_message": "Mensaje",
+    "chat_new_send": "Enviar solicitud",
+    "chat_new_title": "Nueva conversación",
+    "chat_new_zaddr": "Dirección z del destinatario",
+    "chat_select_hint": "Selecciona una conversación para verla.",
+    "chat_send": "Enviar",
+    "chat_send_failed": "no enviado",
+    "chat_waiting_reply": "Esperando a que este contacto responda: podrás escribirle una vez lo haga.",
+    "chat_you": "Tú",
     "choose_icon": "Elegir Icono",
     "clear": "Limpiar",
     "clear_all_bans": "Limpiar Todos los Bloqueos",