feat: 全量功能模块开发与集成测试修复

- 新增后端模块：Alert、APIAsset、Compliance、Lineage、Masking、Risk、SchemaChange、Unstructured、Watermark
- 新增前端模块页面与API接口
- 新增Alembic迁移脚本(002-014)覆盖全量业务表
- 新增测试数据生成脚本与集成测试脚本
- 修复metadata模型JSON类型导入缺失导致启动失败的问题
- 修复前端Alert/APIAsset页面request模块路径错误
- 更新docker-compose与开发计划文档

backend/app/models/watermark.py

@@ -0,0 +1,17 @@
+from datetime import datetime
+from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey
+from sqlalchemy.orm import relationship
+from app.core.database import Base
+
+
+class WatermarkLog(Base):
+    __tablename__ = "watermark_log"
+
+    id = Column(Integer, primary_key=True, index=True)
+    user_id = Column(Integer, ForeignKey("sys_user.id"), nullable=False)
+    export_type = Column(String(20), default="csv")  # csv, excel, txt
+    data_scope = Column(Text)  # JSON: {source_id, table_name, row_count}
+    watermark_key = Column(String(64), nullable=False)  # random key for this export
+    created_at = Column(DateTime, default=datetime.utcnow)
+
+    user = relationship("User")