✨ feat: 数据库基线与通用 DTO（WP-01 第 3、4 步）

- 通用 DTO：Money（最小货币单位整数）、CursorPage 泛型、9 个平台 ID Annotated 类型（前缀+UUIDv7/v4 正则，与 openapi 契约对齐）
- db 基础：naming_convention Base（pk_/uq_/ix_/fk_，AGENTS 8.6）+ async engine + 事务作用域 session
- 首批 6 张表 typed mapping：user/personal_domain/session/service_account/audit_event/outbox_event；Session ID 为 CSPRNG opaque；审计与 Outbox 不可变
- Alembic async 迁移（含表注释）；docker 起 hunjing-postgres 并 upgrade 验证：7 表、约束/索引命名全部符合约定
- 按 database-design skill 清单交叉检查：外键索引全覆盖（复合唯一最左前缀）、审计聚合时间线与 Outbox 投递扫描均为专用复合索引
- 集成测试 8 项（唯一约束、FK restrict/cascade、检查约束、同事务提交）连 PG 测试库运行；pytest 15 项、ruff、mypy strict 全绿

backend/alembic/env.py

@@ -0,0 +1,94 @@
+import asyncio
+from logging.config import fileConfig
+
+from sqlalchemy import pool
+from sqlalchemy.engine import Connection
+from sqlalchemy.ext.asyncio import async_engine_from_config
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# 模型元数据（autogenerate 真源）；连接串来自环境（统一 PostgreSQL，ADR-024）
+import os
+
+from app import models  # noqa: F401  确保模型注册到 metadata
+from app.core.config import get_settings
+from app.db.base import Base
+
+target_metadata = Base.metadata
+db_url = os.environ.get("DATABASE_URL", get_settings().database_url)
+config.set_main_option("sqlalchemy.url", db_url)
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection: Connection) -> None:
+    context.configure(connection=connection, target_metadata=target_metadata)
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations() -> None:
+    """In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    connectable = async_engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    async with connectable.connect() as connection:
+        await connection.run_sync(do_run_migrations)
+
+    await connectable.dispose()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode."""
+
+    asyncio.run(run_async_migrations())
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()