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/zh.json

@@ -110,6 +110,21 @@
     "bootstrap_warning": "现有区块数据（blocks、chainstate、notarizations）将被删除并替换。您的 wallet.dat 不会被修改或删除。",
     "cancel": "取消",
     "characters": "字符",
+    "chat": "聊天",
+    "chat_cancel": "取消",
+    "chat_contact_request": "联系人请求",
+    "chat_empty_hint": "暂无对话。您收到的消息将显示在此处。",
+    "chat_locked_hint": "解锁钱包以加载您的聊天记录。",
+    "chat_new_button": "新建对话",
+    "chat_new_message": "消息",
+    "chat_new_send": "发送请求",
+    "chat_new_title": "新建对话",
+    "chat_new_zaddr": "收款方 z 地址",
+    "chat_select_hint": "选择一个对话以查看。",
+    "chat_send": "发送",
+    "chat_send_failed": "未发送",
+    "chat_waiting_reply": "等待该联系人回复——对方回复后您即可向其发送消息。",
+    "chat_you": "我",
     "choose_icon": "选择图标",
     "clear": "清除",
     "clear_all_bans": "解除所有封禁",