fix(db): using lambda expression to ensure updated_at field (#4730)

* fix(db): 使用 lambda 表达式确保 updated_at 字段正确更新

updated_at 字段原先在 sa_column_kwargs["onupdate"] 中直接使用了 datetime.now()，导致时间戳仅在模块导入时被计算一次，之后不再变化，结果所有记录的更新时间都被设成了程序启动时间。

本次修改将时间戳生成逻辑封装进 lambda 表达式，使 SQLAlchemy 在每次更新记录时才惰性求值，从而保证时间戳实时更新。

* refactor(db): 根据建议引入 TimestampMixin 统一时间戳定义，提取 `created_at`/`updated_at` 至 [TimestampMixin]

astrbot/core/db/po.py

@@ -6,6 +6,14 @@ from typing import TypedDict
 from sqlmodel import JSON, Field, SQLModel, Text, UniqueConstraint
 
 
+class TimestampMixin(SQLModel):
+    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
+    updated_at: datetime = Field(
+        default_factory=lambda: datetime.now(timezone.utc),
+        sa_column_kwargs={"onupdate": lambda: datetime.now(timezone.utc)},
+    )
+
+
 class PlatformStat(SQLModel, table=True):
     """This class represents the statistics of bot usage across different platforms.
 
@@ -30,7 +38,7 @@ class PlatformStat(SQLModel, table=True):
     )
 
 
-class ConversationV2(SQLModel, table=True):
+class ConversationV2(TimestampMixin, SQLModel, table=True):
     __tablename__: str = "conversations"
 
     inner_conversation_id: int | None = Field(
@@ -47,11 +55,7 @@ class ConversationV2(SQLModel, table=True):
     platform_id: str = Field(nullable=False)
     user_id: str = Field(nullable=False)
     content: list | None = Field(default=None, sa_type=JSON)
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
+
     title: str | None = Field(default=None, max_length=255)
     persona_id: str | None = Field(default=None)
     token_usage: int = Field(default=0, nullable=False)
@@ -68,7 +72,7 @@ class ConversationV2(SQLModel, table=True):
     )
 
 
-class PersonaFolder(SQLModel, table=True):
+class PersonaFolder(TimestampMixin, SQLModel, table=True):
     """Persona 文件夹，支持递归层级结构。
 
     用于组织和管理多个 Persona，类似于文件系统的目录结构。
@@ -92,11 +96,6 @@ class PersonaFolder(SQLModel, table=True):
     """父文件夹ID，NULL表示根目录"""
     description: str | None = Field(default=None, sa_type=Text)
     sort_order: int = Field(default=0)
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(
@@ -106,7 +105,7 @@ class PersonaFolder(SQLModel, table=True):
     )
 
 
-class Persona(SQLModel, table=True):
+class Persona(TimestampMixin, SQLModel, table=True):
     """Persona is a set of instructions for LLMs to follow.
 
     It can be used to customize the behavior of LLMs.
@@ -131,11 +130,6 @@ class Persona(SQLModel, table=True):
     """所属文件夹ID，NULL 表示在根目录"""
     sort_order: int = Field(default=0)
     """排序顺序"""
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(
@@ -145,7 +139,7 @@ class Persona(SQLModel, table=True):
     )
 
 
-class Preference(SQLModel, table=True):
+class Preference(TimestampMixin, SQLModel, table=True):
     """This class represents preferences for bots."""
 
     __tablename__: str = "preferences"
@@ -161,11 +155,6 @@ class Preference(SQLModel, table=True):
     """ID of the scope, such as 'global', 'umo', 'plugin_name'."""
     key: str = Field(nullable=False)
     value: dict = Field(sa_type=JSON, nullable=False)
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(
@@ -177,7 +166,7 @@ class Preference(SQLModel, table=True):
     )
 
 
-class PlatformMessageHistory(SQLModel, table=True):
+class PlatformMessageHistory(TimestampMixin, SQLModel, table=True):
     """This class represents the message history for a specific platform.
 
     It is used to store messages that are not LLM-generated, such as user messages
@@ -198,14 +187,9 @@ class PlatformMessageHistory(SQLModel, table=True):
         default=None,
     )  # Name of the sender in the platform
     content: dict = Field(sa_type=JSON, nullable=False)  # a message chain list
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
 
-class PlatformSession(SQLModel, table=True):
+class PlatformSession(TimestampMixin, SQLModel, table=True):
     """Platform session table for managing user sessions across different platforms.
 
     A session represents a chat window for a specific user on a specific platform.
@@ -233,11 +217,6 @@ class PlatformSession(SQLModel, table=True):
     """Display name for the session"""
     is_group: int = Field(default=0, nullable=False)
     """0 for private chat, 1 for group chat (not implemented yet)"""
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(
@@ -247,7 +226,7 @@ class PlatformSession(SQLModel, table=True):
     )
 
 
-class Attachment(SQLModel, table=True):
+class Attachment(TimestampMixin, SQLModel, table=True):
     """This class represents attachments for messages in AstrBot.
 
     Attachments can be images, files, or other media types.
@@ -269,11 +248,6 @@ class Attachment(SQLModel, table=True):
     path: str = Field(nullable=False)  # Path to the file on disk
     type: str = Field(nullable=False)  # Type of the file (e.g., 'image', 'file')
     mime_type: str = Field(nullable=False)  # MIME type of the file
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(
@@ -283,7 +257,7 @@ class Attachment(SQLModel, table=True):
     )
 
 
-class ChatUIProject(SQLModel, table=True):
+class ChatUIProject(TimestampMixin, SQLModel, table=True):
     """This class represents projects for organizing ChatUI conversations.
 
     Projects allow users to group related conversations together.
@@ -310,11 +284,6 @@ class ChatUIProject(SQLModel, table=True):
     """Title of the project"""
     description: str | None = Field(default=None, max_length=1000)
     """Description of the project"""
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(
@@ -338,7 +307,6 @@ class SessionProjectRelation(SQLModel, table=True):
     """Session ID from PlatformSession"""
     project_id: str = Field(nullable=False, max_length=36)
     """Project ID from ChatUIProject"""
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
 
     __table_args__ = (
         UniqueConstraint(
@@ -348,7 +316,7 @@ class SessionProjectRelation(SQLModel, table=True):
     )
 
 
-class CommandConfig(SQLModel, table=True):
+class CommandConfig(TimestampMixin, SQLModel, table=True):
     """Per-command configuration overrides for dashboard management."""
 
     __tablename__ = "command_configs"  # type: ignore
@@ -368,14 +336,9 @@ class CommandConfig(SQLModel, table=True):
     note: str | None = Field(default=None, sa_type=Text)
     extra_data: dict | None = Field(default=None, sa_type=JSON)
     auto_managed: bool = Field(default=False, nullable=False)
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
 
-class CommandConflict(SQLModel, table=True):
+class CommandConflict(TimestampMixin, SQLModel, table=True):
     """Conflict tracking for duplicated command names."""
 
     __tablename__ = "command_conflicts"  # type: ignore
@@ -392,11 +355,6 @@ class CommandConflict(SQLModel, table=True):
     note: str | None = Field(default=None, sa_type=Text)
     extra_data: dict | None = Field(default=None, sa_type=JSON)
     auto_generated: bool = Field(default=False, nullable=False)
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
-    updated_at: datetime = Field(
-        default_factory=lambda: datetime.now(timezone.utc),
-        sa_column_kwargs={"onupdate": datetime.now(timezone.utc)},
-    )
 
     __table_args__ = (
         UniqueConstraint(