feat(m0): 后端骨架 + Web/安卓前端骨架 + 设计文档

- backend: FastAPI 应用工厂、统一错误信封、JWT、短信登录、工作区/成员/邀请、幂等中间件
- alembic 0001: workspace/member/invitation/audit_log/app_user + RLS 策略 + 双角色 GRANT
- tests: 认证/工作区/租户隔离/幂等 四组用例（尚未在本机执行）
- web: React18+Vite 骨架（登录、工作区、邀请落地页）
- android: Compose 骨架（登录、工作区列表）
- 2.Design: PRODUCT-PLAN / ROADMAP-M0-M1 / NAMING / DEVELOPMENT

backend/app/audit.py

@@ -0,0 +1,35 @@
+"""审计日志写入。所有敏感操作（建工作区、邀请、加入、移除成员）都要留痕。"""
+
+from __future__ import annotations
+
+import uuid
+from typing import Any
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from .models import AuditLog
+
+
+async def record(
+    session: AsyncSession,
+    *,
+    workspace_id: uuid.UUID | None,
+    actor_user_id: uuid.UUID | None,
+    action: str,
+    target_type: str = "",
+    target_id: str = "",
+    payload: dict[str, Any] | None = None,
+    ip: str = "",
+) -> None:
+    session.add(
+        AuditLog(
+            workspace_id=workspace_id,
+            actor_user_id=actor_user_id,
+            action=action,
+            target_type=target_type,
+            target_id=target_id,
+            payload=payload or {},
+            ip=ip,
+        )
+    )
+    await session.flush()