feat(ai-chat): 聊天 UI 配置 V3 — 名称/头像/时间配置项消费

- CHAT_UI_DEFAULTS 同步后端 4 新键 (show_name/show_avatar/avatar/time_format/time_humanize)
- 标题与 AI 头像按开关显隐, 自定义头像 (素材库 pic_path / URL) 优先于内置
- formatTime 支持 auto(智能分段)/full(完整) 与 humanizeTime 相对时间优先 (刚刚/N分钟前/N小时前/昨天/前天/M月D日/Y年M月D日)
- i18n 中英各+5 键

lang/en-us/ai-chat/index.js

@@ -12,6 +12,12 @@ export const lang = {
 	timeFormatToday: 'Today',
 	timeFormatYesterday: 'Yesterday',
 	timeFormatBeforeYesterday: 'Day before yesterday',
+	// PR-CHAT-UI-CONFIG-V3 (2026-09-24): Humanized relative time (ui_time_humanize)
+	timeJustNow: 'Just now',
+	timeMinutesAgo: '{n} min ago',
+	timeHoursAgo: '{n} h ago',
+	timeMonthDay: '{m}/{d}',
+	timeYearMonthDay: '{y}/{m}/{d}',
 
 	// ====== ai-chat-message ======
 	aiNickname: 'AI Assistant',