feat(ai): V2 深度增强 — SSE 流式/全局助手/内容安全/多角色覆盖

对标 Khanmigo/Duolingo Max/Squirrel AI/Century Tech 实现：

- SSE 流式响应：createAiChatCompletionStream AsyncGenerator + /api/ai/chat/stream SSE 端点 + useAiChatStream hook（AbortController 停止生成 + localStorage 持久化）

- Markdown 渲染：AiMarkdownRenderer（react-markdown + remark-gfm + 代码块/表格/列表 + hover 复制按钮）

- 全局 AI 助手：AiAssistantWidget 浮动按钮 + Sheet 侧抽屉 + usePathname 路由推断上下文（7 类场景系统提示）+ dashboard layout 全局注入 AiClientProvider

- 内容安全：content-safety.ts 多层过滤（输入/输出安全过滤 + 每日限制 student 50/teacher 200/parent 30/admin 500 + 学生苏格拉底模式），COPPA/FERPA K12 合规

- 多角色 AI 覆盖：家长端 AiChildSummary（学情摘要）+ 管理员端 AiUsageDashboard（使用监控）+ 学生端 AiStudyPath（个性化学习路径）

- i18n 修复：8 处错误键引用 + zh-CN/en ai.json 全面扩展

- 架构文档 004/005 同步更新

src/shared/i18n/messages/zh-CN/ai.json

@@ -5,8 +5,20 @@
     "inputLabel": "消息输入",
     "send": "发送",
     "thinking": "AI 正在思考...",
+    "streaming": "AI 正在输入...",
+    "stopGeneration": "停止生成",
     "maxReached": "已达到最大消息数",
-    "clear": "清空对话"
+    "clear": "清空对话",
+    "clearConfirm": "确认清空所有消息？",
+    "copy": "复制",
+    "copied": "已复制！",
+    "suggestedPrompts": {
+      "title": "试试问我...",
+      "teacher": ["帮我批改这道题", "生成一个课堂活动", "创建一道测验题"],
+      "student": ["解释这个概念", "给我一道练习题", "帮我复习"],
+      "parent": ["我孩子学得怎么样？", "在家应该关注什么？"],
+      "admin": ["显示 AI 使用统计", "哪些老师最常使用 AI？"]
+    }
   },
   "provider": {
     "label": "AI 服务商",
@@ -28,10 +40,13 @@
     "loaded": "建议已加载",
     "selected": "已选择建议",
     "select": "选择",
-    "difficulty": "难度"
+    "difficulty": "难度",
+    "practiceNow": "立即练习",
+    "addAll": "全部添加"
   },
   "grading": {
     "title": "AI 批改建议",
+    "description": "AI 驱动的主观题评分与反馈",
     "suggestedScore": "建议分数",
     "confidence": "置信度",
     "feedback": "反馈",
@@ -40,7 +55,13 @@
     "applyFeedback": "应用反馈",
     "loading": "AI 批改中...",
     "error": "AI 批改失败",
-    "notAvailable": "此题型不支持 AI 批改"
+    "notAvailable": "此题型不支持 AI 批改",
+    "batchTitle": "批量 AI 批改",
+    "batchDescription": "一次性为所有主观题生成 AI 建议",
+    "batchGenerate": "生成全部建议",
+    "batchProgress": "处理中 {done}/{total}",
+    "currentScore": "当前分数",
+    "scoreDifference": "差值"
   },
   "errorBook": {
     "similarQuestions": "相似题目",
@@ -56,11 +77,18 @@
   },
   "lessonPrep": {
     "generateContent": "生成内容",
+    "description": "AI 驱动的教学内容生成",
     "generateActivity": "建议活动",
     "generateAssessment": "生成评估",
     "generateQuestion": "生成讨论题",
     "loading": "生成中...",
-    "error": "内容生成失败"
+    "error": "内容生成失败",
+    "additionalContext": "附加上下文",
+    "additionalContextPlaceholder": "添加特定要求或上下文信息...",
+    "insertContent": "插入内容",
+    "editBeforeInsert": "插入前编辑",
+    "history": "生成历史",
+    "clearHistory": "清空历史"
   },
   "exam": {
     "generate": "生成",
@@ -81,7 +109,64 @@
     "sourceTextPlaceholder": "粘贴试卷文本以解析为题目",
     "sourceTextDesc": "AI 将从文本中提取题目和结构。",
     "generationTitle": "AI 生成",
-    "generationDesc": "粘贴试卷文本并生成结构化预览。"
+    "generationDesc": "粘贴试卷文本并生成结构化预览。",
+    "variantType": {
+      "label": "变体类型",
+      "same_knowledge_point": "同知识点，不同情境",
+      "different_difficulty": "不同难度",
+      "different_format": "不同题型"
+    },
+    "targetDifficulty": "目标难度",
+    "addVariant": "添加变体"
+  },
+  "parent": {
+    "summary": "AI 学情摘要",
+    "summaryDescription": "AI 生成的子女学习进度概览",
+    "generateSummary": "生成摘要",
+    "weaknessHint": "需关注领域",
+    "suggestion": "家庭辅导建议",
+    "loading": "生成摘要中...",
+    "error": "生成摘要失败"
+  },
+  "admin": {
+    "usageDashboard": "AI 使用仪表盘",
+    "dashboardDescription": "监控全校 AI 使用情况",
+    "totalCalls": "AI 调用总数",
+    "activeUsers": "活跃用户",
+    "costEstimate": "预估成本",
+    "topUsers": "高频用户",
+    "byCapability": "按能力分类",
+    "byRole": "按角色分类",
+    "recentActivity": "最近活动",
+    "noData": "暂无 AI 使用数据",
+    "callsToday": "今日调用",
+    "callsThisWeek": "本周调用",
+    "errorRate": "错误率",
+    "avgDuration": "平均耗时"
+  },
+  "studyPath": {
+    "title": "你的学习路径",
+    "description": "AI 个性化学习建议",
+    "nextSteps": "推荐下一步",
+    "mastered": "已掌握",
+    "inProgress": "学习中",
+    "needsWork": "需要加强",
+    "generate": "生成学习路径",
+    "loading": "生成学习路径中...",
+    "error": "生成学习路径失败",
+    "startLearning": "开始学习"
+  },
+  "widget": {
+    "title": "AI 助手",
+    "open": "打开 AI 助手",
+    "close": "关闭",
+    "contextAware": "上下文感知"
+  },
+  "safety": {
+    "blocked": "您的消息被安全过滤器拦截，请保持教育性对话。",
+    "dailyLimit": "今日 AI 使用次数已达上限，请明天再试。",
+    "studentMode": "AI 处于学生模式，将引导你自主找到答案。",
+    "contentFiltered": "AI 回复中的不当内容已被过滤。"
   },
   "error": {
     "invalidInput": "输入数据无效",
@@ -104,6 +189,8 @@
     "lessonContent": "AI 备课内容",
     "questionVariant": "AI 题目变体",
     "similarQuestion": "AI 相似题",
-    "weaknessAnalysis": "AI 薄弱点分析"
+    "weaknessAnalysis": "AI 薄弱点分析",
+    "childSummary": "AI 子女摘要",
+    "studyPath": "AI 学习路径"
   }
 }