feat(ux): epic UX design improvements across agents, chat, notes, and i18n

Comprehensive UI/UX updates including agent card redesign, chat container
improvements, note editor enhancements, memory echo notifications, and
updated translations for all 15 locales.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

keep-notes/locales/zh.json

@@ -1383,7 +1383,8 @@
     "renameError": "重命名时出错",
     "welcome": "我可以帮助您综合笔记、生成新想法或讨论您的笔记本。",
     "searching": "搜索中...",
-    "noNotesFoundForContext": "未找到与此问题相关的笔记。请用你的常识回答。"
+    "noNotesFoundForContext": "未找到与此问题相关的笔记。请用你的常识回答。",
+    "webSearch": "网络搜索"
   },
   "labHeader": {
     "title": "实验室",