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/core/config.py

@@ -10,6 +10,11 @@ class Settings(BaseSettings):
     DATABASE_URL: str = "postgresql+psycopg2://pdg:pdg_secret_2024@localhost:5432/prop_data_guard"
     REDIS_URL: str = "redis://localhost:6379/0"
 
+    # Database password encryption key (Fernet-compatible base64, 32 bytes)
+    # If empty, will be derived from SECRET_KEY for backward compatibility.
+    # STRONGLY recommended to set this explicitly in production.
+    DB_ENCRYPTION_KEY: str = ""
+
     SECRET_KEY: str = "prop-data-guard-super-secret-key-change-in-production"
     ALGORITHM: str = "HS256"
     ACCESS_TOKEN_EXPIRE_MINUTES: int = 30