feat(data-ana): v2 P6 硬化完成 + 6 新 RPC + Prometheus 监控

P6 硬化（5 项全部完成）:

- CDC 多实例水平扩展: _INSTANCE_ID + get_lag() 真实 lag 计算

- ExamCache Redis 化: key data_ana:exam:{exam_id}, TTL 30 天 + 内存 LRU fallback

- ClickHouse TTL 归档: 5 表均加 TTL（1-3 年），分区级删除

- Prometheus 监控: 18 个指标（CDC/CH/ExamCache/DataScope/gRPC/业务）

- readyz 深度硬化: 4 依赖超时检查（CH 1s/Redis 200ms/iam 2s/CDC lag<1000）

v2 新增 6 个 RPC（analytics.proto 扩展为 18 RPC）:

- GetStudentGrowth / GetAssignmentAnalysis / GetMasterySummary

- ListDiagnosticReports（占位，待 ai 服务）/ ListErrorBookItems / GetErrorBookStats

监控与可观测性: lifespan 预热 + gRPC ServerInterceptor + CDC 消费者指标

Docker 本地测试 19 项全部通过（healthz/readyz/metrics + 11 HTTP + 10 gRPC + ruff）

nextstep-v2.md: 上游需求对齐 + 下游要求（iam/core-edu/content/ai/SRE）

packages/shared-proto/proto/analytics.proto

@@ -30,6 +30,20 @@ service AnalyticsService {
   rpc GetStudentMastery(GetStudentMasteryRequest) returns (StudentMastery);
   // 订阅掌握度更新（server-streaming，P5+ AI 个性化推荐实时推送通道）.
   rpc SubscribeMasteryUpdate(SubscribeMasteryUpdateRequest) returns (stream MasteryUpdateEvent);
+
+  // ===== P6+ v2 扩展 RPC（响应上游 parent-bff / student-bff v2 请求） =====
+  // 学生成长档案（综合成绩趋势 + 掌握度变化 + 考勤统计，供 parent-bff GrowthArchiveService）.
+  rpc GetStudentGrowth(GetStudentGrowthRequest) returns (StudentGrowth);
+  // 作业/考试分析（单次作业/考试维度统计，供 student-bff / parent-bff）.
+  rpc GetAssignmentAnalysis(GetAssignmentAnalysisRequest) returns (AssignmentAnalysis);
+  // 学生掌握度汇总（轻量级，仅返回总体掌握度 + 三档分布，供 parent-bff MasteryService.GetSummary）.
+  rpc GetMasterySummary(GetMasterySummaryRequest) returns (MasterySummary);
+  // 诊断报告列表（占位实现，真实数据需 ai 服务集成，供 parent-bff / student-bff）.
+  rpc ListDiagnosticReports(ListDiagnosticReportsRequest) returns (DiagnosticReportList);
+  // 错题本列表（gRPC 版本，供 parent-bff ErrorBookService.List）.
+  rpc ListErrorBookItems(ListErrorBookItemsRequest) returns (ErrorBookList);
+  // 错题本统计（按知识点聚合，供 parent-bff ErrorBookService.GetStats）.
+  rpc GetErrorBookStats(GetErrorBookStatsRequest) returns (ErrorBookStats);
 }
 
 // ===== 请求消息 =====
@@ -101,6 +115,44 @@ message SubscribeMasteryUpdateRequest {
   string class_id = 2; // 可选，订阅指定班级全部学生
 }
 
+// ===== P6+ v2 扩展 RPC 请求消息 =====
+
+message GetStudentGrowthRequest {
+  string student_id = 1;
+  int64 start_date = 2; // Unix timestamp（秒）
+  int64 end_date = 3;
+  string subject_id = 4; // 可选
+}
+
+message GetAssignmentAnalysisRequest {
+  string class_id = 1;
+  string assignment_id = 2; // exam_id 或 homework_id
+  string subject_id = 3; // 可选
+}
+
+message GetMasterySummaryRequest {
+  string student_id = 1;
+  string subject_id = 2; // 可选
+}
+
+message ListDiagnosticReportsRequest {
+  string student_id = 1;
+  int64 since = 2; // Unix timestamp（秒）
+  int32 limit = 3; // 默认 10
+}
+
+message ListErrorBookItemsRequest {
+  string student_id = 1;
+  string subject_id = 2; // 可选，按学科过滤
+  int32 limit = 3; // 默认 100
+  int32 offset = 4; // 分页偏移
+}
+
+message GetErrorBookStatsRequest {
+  string student_id = 1;
+  string subject_id = 2; // 可选
+}
+
 // ===== 响应消息 =====
 
 message ClassPerformance {
@@ -260,3 +312,111 @@ message MasteryUpdateEvent {
   double previous_level = 5;
   int64 calculated_at = 6; // Unix timestamp（秒）
 }
+
+// ===== P6+ v2 扩展 RPC 响应消息 =====
+
+message StudentGrowth {
+  string student_id = 1;
+  // 成绩趋势（来自 LearningTrend）
+  repeated TrendPoint score_trend = 2;
+  // 掌握度变化趋势（按时间排序的快照）
+  repeated MasteryTrendPoint mastery_trend = 3;
+  // 考勤统计
+  AttendanceSummary attendance = 4;
+  // 总体成长评分（综合分数、掌握度、考勤计算）
+  double growth_score = 5;
+  // 成长等级（excellent / good / average / needs_improvement）
+  string growth_level = 6;
+}
+
+message MasteryTrendPoint {
+  int64 calculated_at = 1;
+  double overall_mastery = 2;
+}
+
+message AttendanceSummary {
+  int32 total_days = 1;
+  int32 present_days = 2;
+  int32 absent_days = 3;
+  int32 late_days = 4;
+  double attendance_rate = 5; // 出勤率 0.0-1.0
+}
+
+message AssignmentAnalysis {
+  string assignment_id = 1;
+  string class_id = 2;
+  string subject_id = 3;
+  double average_score = 4;
+  double highest_score = 5;
+  double lowest_score = 6;
+  int32 total_students = 7;
+  int32 submitted_count = 8;
+  double pass_rate = 9; // 及格率
+  // 分数段分布（90-100 / 80-89 / 70-79 / 60-69 / <60）
+  repeated ScoreRange ranges = 10;
+}
+
+message ScoreRange {
+  string label = 1; // "90-100" / "80-89" etc.
+  int32 count = 2;
+  double percentage = 3; // 占比 0.0-1.0
+}
+
+message MasterySummary {
+  string student_id = 1;
+  double overall_mastery = 2; // 0.0-1.0
+  int32 mastered_count = 3; // mastery >= 0.8
+  int32 progressing_count = 4; // 0.4 <= mastery < 0.8
+  int32 weak_count = 5; // mastery < 0.4
+  int32 total_knowledge_points = 6;
+  string mastery_level = 7; // mastered / progressing / weak（总体）
+}
+
+message DiagnosticReportList {
+  string student_id = 1;
+  repeated DiagnosticReport reports = 2;
+  int32 total = 3;
+}
+
+message DiagnosticReport {
+  string report_id = 1;
+  string student_id = 2;
+  string report_type = 3; // KNOWLEDGE_GAP / LEARNING_STYLE / WEAKNESS_ANALYSIS
+  string title = 4;
+  string summary = 5; // 报告摘要
+  int64 generated_at = 6; // Unix timestamp（秒）
+  string status = 7; // pending / completed / failed
+}
+
+message ErrorBookList {
+  string student_id = 1;
+  repeated ErrorBookItem items = 2;
+  int32 total = 3;
+}
+
+message ErrorBookItem {
+  string question_id = 1;
+  string knowledge_point_id = 2;
+  string knowledge_point_title = 3;
+  int32 error_count = 4;
+  int64 last_error_time = 5; // Unix timestamp（秒）
+  string content = 6; // 题目内容摘要
+}
+
+message ErrorBookStats {
+  string student_id = 1;
+  int32 total_error_questions = 2;
+  int32 total_error_count = 3; // 总错误次数
+  // 按知识点聚合的错题统计
+  repeated KnowledgePointErrorStats by_knowledge_point = 4;
+  // 最近 7 天错误次数
+  int32 recent_7d_errors = 5;
+}
+
+message KnowledgePointErrorStats {
+  string knowledge_point_id = 1;
+  string title = 2;
+  int32 error_count = 3;
+  int32 question_count = 4;
+  double error_rate = 5; // 错误率 0.0-1.0
+}