chore: initial commit — leaudit-platform project skeleton

17-table PostgreSQL schema with full Chinese column comments,
FastAPI project structure (admin/common/modules),
DSL rule files, and schema migration scripts.

fastapi_common/fastapi_common_sqlalchemy/base.py

@@ -0,0 +1,10 @@
+"""SQLAlchemy 声明式基类。"""
+
+from __future__ import annotations
+
+from sqlalchemy.orm import DeclarativeBase
+
+
+class Base(DeclarativeBase):
+    """SQLAlchemy 声明式基类。"""
+    pass