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/ko.json

@@ -110,6 +110,21 @@
     "bootstrap_warning": "기존 블록 데이터(blocks, chainstate, notarizations)가 삭제되고 교체됩니다. wallet.dat는 수정되거나 삭제되지 않습니다.",
     "cancel": "취소",
     "characters": "문자",
+    "chat": "채팅",
+    "chat_cancel": "취소",
+    "chat_contact_request": "연락 요청",
+    "chat_empty_hint": "아직 대화가 없습니다. 받은 메시지가 여기에 표시됩니다.",
+    "chat_locked_hint": "채팅을 불러오려면 지갑 잠금을 해제하세요.",
+    "chat_new_button": "새 대화",
+    "chat_new_message": "메시지",
+    "chat_new_send": "요청 보내기",
+    "chat_new_title": "새 대화",
+    "chat_new_zaddr": "받는 사람 z-주소",
+    "chat_select_hint": "볼 대화를 선택하세요.",
+    "chat_send": "전송",
+    "chat_send_failed": "전송 안 됨",
+    "chat_waiting_reply": "상대방의 답장을 기다리는 중입니다 — 답장하면 메시지를 보낼 수 있습니다.",
+    "chat_you": "나",
     "choose_icon": "아이콘 선택",
     "clear": "지우기",
     "clear_all_bans": "모든 차단 해제",