feat(mixin): add TableBaseMixin and UUIDTableBaseMixin for async CRUD operations

- Implemented TableBaseMixin providing generic CRUD methods and automatic timestamp management.
- Introduced UUIDTableBaseMixin for models using UUID as primary keys.
- Added ListResponse for standardized paginated responses.
- Created TimeFilterRequest and PaginationRequest for filtering and pagination parameters.
- Enhanced get_with_count method to return both item list and total count.
- Included validation for time filter parameters in TimeFilterRequest.
- Improved documentation and usage examples throughout the code.

models/mixin/__init__.py

@@ -0,0 +1,46 @@
+"""
+SQLModel Mixin模块
+
+提供各种Mixin类供SQLModel实体使用。
+
+包含：
+- polymorphic: 联表继承工具（create_subclass_id_mixin, AutoPolymorphicIdentityMixin, PolymorphicBaseMixin）
+- table: 表基类（TableBaseMixin, UUIDTableBaseMixin）
+- table: 查询参数类（TimeFilterRequest, PaginationRequest, TableViewRequest）
+- jwt/: JWT认证相关（JWTAuthMixin, JWTManager, JWTKey等）- 需要时直接从 .jwt 导入
+- info_response: InfoResponse DTO的id/时间戳Mixin
+
+导入顺序很重要，避免循环导入：
+1. polymorphic（只依赖 SQLModelBase）
+2. table（依赖 polymorphic）
+
+注意：jwt 模块不在此处导入，因为 jwt/manager.py 导入 ServerConfig，
+而 ServerConfig 导入本模块，会形成循环。需要 jwt 功能时请直接从 .jwt 导入。
+"""
+# polymorphic 必须先导入
+from .polymorphic import (
+    create_subclass_id_mixin,
+    AutoPolymorphicIdentityMixin,
+    PolymorphicBaseMixin,
+)
+# table 依赖 polymorphic
+from .table import (
+    TableBaseMixin,
+    UUIDTableBaseMixin,
+    TimeFilterRequest,
+    PaginationRequest,
+    TableViewRequest,
+    ListResponse,
+    T,
+    now,
+    now_date,
+)
+# jwt 不在此处导入（避免循环：jwt/manager.py → ServerConfig → mixin → jwt）
+# 需要时直接从 sqlmodels.mixin.jwt 导入
+from .info_response import (
+    IntIdInfoMixin,
+    UUIDIdInfoMixin,
+    DatetimeInfoMixin,
+    IntIdDatetimeInfoMixin,
+    UUIDIdDatetimeInfoMixin,
+)