feat(p4): content analysis service with Neo4j knowledge graph and ClickHouse analytics

P4 阶段交付物：
- services/content: 内容资源服务（NestJS）
  - textbooks: 教材 CRUD + 知识图谱绑定
  - config/neo4j.ts: Neo4j driver 单例
  - textbooks.service.ts: MySQL CRUD + Neo4j 知识图谱（createKnowledgeGraph/getPrerequisites）
  - package.json: 补充 @opentelemetry/sdk-node + exporter-trace-otlp-http
- services/data-ana: 数据分析服务（Python FastAPI）
  - main.py: FastAPI + /healthz + class_performance + student_weakness 骨架
  - clickhouse_client.py: ClickHouse 客户端封装
  - config.py: 环境变量配置
- packages/shared-proto/proto/content.proto: TextbookService + KnowledgeGraphService 契约
- packages/shared-proto/proto/analytics.proto: AnalyticsService 契约（class_performance/student_weakness）

services/data-ana/pyproject.toml

@@ -0,0 +1,24 @@
+[project]
+name = "data-ana-service"
+version = "0.1.0"
+description = "数据分析服务 - ClickHouse + 学习分析"
+requires-python = ">=3.12"
+dependencies = [
+    "fastapi>=0.115.0",
+    "uvicorn[standard]>=0.30.0",
+    "clickhouse-connect>=0.7.0",
+    "pydantic>=2.9.0",
+    "pydantic-settings>=2.5.0",
+    "opentelemetry-api>=1.27.0",
+    "opentelemetry-sdk>=1.27.0",
+    "opentelemetry-instrumentation-fastapi>=0.48b0",
+    "prometheus-client>=0.20.0",
+    "structlog>=24.4.0",
+]
+
+[tool.ruff]
+line-length = 100
+target-version = "py312"
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "N", "W", "UP", "B", "SIM"]