i18n(chat): translate chat_toast_too_long (8 languages)

The one remaining English-only chat string (the "message too long" toast from
the larger-messages composer cap) is now translated into de/es/fr/pt/ru/zh/ja/ko
(2503 -> 2504 keys each), consistent with each file's terminology and formality.
No new CJK glyphs — all covered by the existing subset font.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

res/lang/zh.json

@@ -387,6 +387,7 @@
     "chat_toast_not_connected": "未连接——聊天消息未发送。",
     "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_too_long": "消息过长——请缩短后重新发送。",
     "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_today": "今天",
     "chat_ts_12h": "12小时",