i18n(chat): translate the new chat-backlog strings (8 languages)

Translate the 14 chat strings added by the backlog work (relative time, retry,
jump-to-latest, empty states, search, export, message-too-long, mute/unmute) into
de/es/fr/ja/ko/pt/ru/zh, added additively (no existing key overwritten).

Also fix a key collision the English pass introduced: the new empty-state
sub-hint reused "chat_empty_hint", which already meant the standalone list hint —
so English and the translations disagreed. Split it into a distinct
"chat_empty_start" for the "Start one with New conversation" sub-line, leaving
the original chat_empty_hint intact.

Rebuilt the CJK subset font: +3 glyphs (刚静音) for zh "刚刚"/"静音", 0 removed.

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

res/lang/zh.json

@@ -140,16 +140,29 @@
     "chat_contact_added": "已添加联系人——可在联系人中重命名",
     "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_empty_start": "点击\"新建会话\"开始。",
+    "chat_empty_title": "还没有会话",
+    "chat_export": "导出聊天…",
+    "chat_export_done": "会话已导出",
+    "chat_export_failed": "无法写入导出文件。",
+    "chat_export_warn": "将解密后的消息保存为纯文本。请妥善保管该文件。",
+    "chat_jump_latest": "最新",
+    "chat_len_over": "消息过长",
     "chat_locked_hint": "解锁钱包以加载您的聊天记录。",
+    "chat_mute": "静音",
     "chat_new_button": "新建对话",
     "chat_new_message": "消息",
     "chat_new_message_toast": "新的加密聊天消息",
     "chat_new_send": "发送请求",
     "chat_new_title": "新建对话",
     "chat_new_zaddr": "收款方 z 地址",
+    "chat_no_matches": "没有与搜索匹配的会话。",
+    "chat_retry": "重试",
+    "chat_search": "搜索会话",
     "chat_select_hint": "选择一个对话以查看。",
     "chat_send": "发送",
     "chat_send_failed": "未发送",
+    "chat_time_now": "刚刚",
     "chat_toast_compose_failed": "无法编写该消息（内容过长？）。",
     "chat_toast_lite_busy": "已有发送正在进行中，或未打开任何钱包。",
     "chat_toast_no_zaddr": "没有可用于发送聊天的 z 地址。",
@@ -157,6 +170,7 @@
     "chat_toast_request_compose_failed": "无法编写联系人请求（地址或文本无效？）。",
     "chat_toast_request_queued": "联系人请求已排队。",
     "chat_toast_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_unmute": "取消静音",
     "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",