重构: 前端DRY(style全局沉淀 + ts/js公共沉淀)

style-dry:
- 新增 src/styles/components.css: .info-item*/.panel/.panel-header/.tech-tag/.card-tags 全局
- main.ts 注册 import
- 删重复: ProjectDetail/TaskDetail/TaskOutputCard/ProjectCard/Projects(scoped删重复, 全局对子组件生效)
- 未使用清理: Projects .card-progress dead(1处保守核对)

tsjs-dry:
- aiShared.ts: resolveAiLang(合并useAiSend.resolveLang + useAiContext.resolveLanguage)
- stores/knowledge.ts: kindText/kindLabel/kindIcon/knowledgeStatusLabel/knowledgeConfidenceLabel(5公共)
- 删重复: useAiSend/useAiContext(resolveLang) + Knowledge/KnowledgeDetail(4+5 helper) + ActiveProjectsPanel(formatLastActivity→formatRelativeZh复用)

strategy: DRY收口, 公共沉淀(utils/store/shared); relativeTime非纯重复保留; .btn/.empty-hint局部override WATCH未动

src/composables/ai/aiShared.ts

@@ -12,11 +12,30 @@
 
 import { aiApi } from '@/api'
 import { state } from '@/stores/ai'
+import { useAppSettingsStore } from '@/stores/appSettings'
 import i18n from '@/i18n'
 import type { AiToolCallInfo } from '@/api/types'
 
+const appSettings = useAppSettingsStore()
+
 const t = ((i18n as any).global.t as (k: string, named?: Record<string, unknown>) => string).bind((i18n as any).global)
 
+/**
+ * 解析 AI 回复语言(useAiSend.sendMessage / useAiContext.compressContext 共用)。
+ *
+ * df-ai-language='auto' → 回落到 df-language(应用主语言);否则用 df-ai-language 指定值;
+ * 兜底 'zh-CN'。
+ *
+ * 原分别在 useAiSend.resolveLang(三元)与 useAiContext.resolveLanguage(if/else)各一份,
+ * 语义相同仅写法不同,提取至此共用。
+ */
+export function resolveAiLang(): string {
+  const raw = appSettings.get<string>('df-ai-language', 'auto')
+  return raw === 'auto'
+    ? appSettings.get<string>('df-language', 'zh-CN')
+    : raw
+}
+
 /** 客户端消息自增 id(全局唯一,多个 composable 共用 nextMsgId) */
 let _msgCounter = 0