feat: Enhance models and README with additional features and improvements

- Updated README to include KodBox in project vision.
- Added model descriptions for clarity in Download, File, Folder, Group, Node, Order, Policy, Redeem, Report, Request, Response, Setting, Share, SourceLink, StoragePack, Tag, Task, User, and WebDAV.
- Changed optional fields from Optional[...] to the new union type syntax (e.g., str | None).
- Improved foreign key references in models for consistency.
- Refactored relationships in models to use singular forms where appropriate.
- Updated login service to reflect changes in request model types.

models/file.py

@@ -1,8 +1,7 @@
 
-from typing import Optional, TYPE_CHECKING
+from typing import TYPE_CHECKING
 from sqlmodel import Field, Relationship, UniqueConstraint, CheckConstraint, Index
 from .base import TableBase
-from datetime import datetime
 
 if TYPE_CHECKING:
     from .user import User
@@ -11,7 +10,6 @@ if TYPE_CHECKING:
     from .source_link import SourceLink
 
 class File(TableBase, table=True):
-    __tablename__ = 'files'
     __table_args__ = (
         UniqueConstraint("folder_id", "name", name="uq_file_folder_name_active"),
         CheckConstraint("name NOT LIKE '%/%' AND name NOT LIKE '%\\%'", name="ck_file_name_no_slash"),
@@ -21,18 +19,18 @@ class File(TableBase, table=True):
     )
 
     name: str = Field(max_length=255, description="文件名")
-    source_name: Optional[str] = Field(default=None, description="源文件名")
+    source_name: str | None = Field(default=None, description="源文件名")
     size: int = Field(default=0, sa_column_kwargs={"server_default": "0"}, description="文件大小（字节）")
-    upload_session_id: Optional[str] = Field(default=None, max_length=255, unique=True, index=True, description="分块上传会话ID")
-    file_metadata: Optional[str] = Field(default=None, description="文件元数据 (JSON格式)") # 后续可以考虑模型继承？
+    upload_session_id: str | None = Field(default=None, max_length=255, unique=True, index=True, description="分块上传会话ID")
+    file_metadata: str | None = Field(default=None, description="文件元数据 (JSON格式)") # 后续可以考虑模型继承？
     
     # 外键
-    user_id: int = Field(foreign_key="users.id", index=True, description="所属用户ID")
-    folder_id: int = Field(foreign_key="folders.id", index=True, description="所在目录ID")
-    policy_id: int = Field(foreign_key="policies.id", index=True, description="所属存储策略ID")
+    user_id: int = Field(foreign_key="user.id", index=True, description="所属用户ID")
+    folder_id: int = Field(foreign_key="folder.id", index=True, description="所在目录ID")
+    policy_id: int = Field(foreign_key="policy.id", index=True, description="所属存储策略ID")
     
     # 关系
-    user: list["User"] = Relationship(back_populates="files")
-    folder: list["Folder"] = Relationship(back_populates="files")
-    policy: list["Policy"] = Relationship(back_populates="files")
+    user: "User" = Relationship(back_populates="files")
+    folder: "Folder" = Relationship(back_populates="files")
+    policy: "Policy" = Relationship(back_populates="files")
     source_links: list["SourceLink"] = Relationship(back_populates="file")