✨ 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/script.py.mako

@@ -0,0 +1,28 @@
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, Sequence[str], None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}