feat: add models for physical files, policies, and user management

- Implement PhysicalFile model to manage physical file references and reference counting.
- Create Policy model with associated options and group links for storage policies.
- Introduce Redeem and Report models for handling redeem codes and reports.
- Add Settings model for site configuration and user settings management.
- Develop Share model for sharing objects with unique codes and associated metadata.
- Implement SourceLink model for managing download links associated with objects.
- Create StoragePack model for managing user storage packages.
- Add Tag model for user-defined tags with manual and automatic types.
- Implement Task model for managing background tasks with status tracking.
- Develop User model with comprehensive user management features including authentication.
- Introduce UserAuthn model for managing WebAuthn credentials.
- Create WebDAV model for managing WebDAV accounts associated with users.

sqlmodels/physical_file.py

@@ -0,0 +1,91 @@
+"""
+物理文件模型
+
+表示磁盘上的实际文件。多个 Object 可以引用同一个 PhysicalFile，
+实现文件共享而不复制物理文件。
+
+引用计数逻辑：
+- 每个引用此文件的 Object 都会增加引用计数
+- 当 Object 被删除时，减少引用计数
+- 只有当引用计数为 0 时，才物理删除文件
+"""
+from typing import TYPE_CHECKING
+from uuid import UUID
+
+from sqlalchemy import BigInteger
+from sqlmodel import Field, Relationship, Index
+
+from .base import SQLModelBase
+from .mixin import UUIDTableBaseMixin
+
+if TYPE_CHECKING:
+    from .object import Object
+    from .policy import Policy
+
+
+class PhysicalFileBase(SQLModelBase):
+    """物理文件基础模型"""
+
+    storage_path: str = Field(max_length=512)
+    """物理存储路径（相对于存储策略根目录）"""
+
+    size: int = Field(default=0, sa_type=BigInteger)
+    """文件大小（字节）"""
+
+    checksum_md5: str | None = Field(default=None, max_length=32)
+    """MD5校验和（用于文件去重和完整性校验）"""
+
+
+class PhysicalFile(PhysicalFileBase, UUIDTableBaseMixin):
+    """
+    物理文件模型
+
+    表示磁盘上的实际文件。多个 Object 可以引用同一个 PhysicalFile，
+    实现文件共享而不复制物理文件。
+    """
+
+    __table_args__ = (
+        Index("ix_physical_file_policy_path", "policy_id", "storage_path"),
+        Index("ix_physical_file_checksum", "checksum_md5"),
+    )
+
+    policy_id: UUID = Field(
+        foreign_key="policy.id",
+        index=True,
+        ondelete="RESTRICT",
+    )
+    """存储策略UUID"""
+
+    reference_count: int = Field(default=1, ge=0)
+    """引用计数（有多少个 Object 引用此物理文件）"""
+
+    # 关系
+    policy: "Policy" = Relationship()
+    """存储策略"""
+
+    objects: list["Object"] = Relationship(back_populates="physical_file")
+    """引用此物理文件的所有逻辑对象"""
+
+    def increment_reference(self) -> int:
+        """
+        增加引用计数
+
+        :return: 更新后的引用计数
+        """
+        self.reference_count += 1
+        return self.reference_count
+
+    def decrement_reference(self) -> int:
+        """
+        减少引用计数
+
+        :return: 更新后的引用计数
+        """
+        if self.reference_count > 0:
+            self.reference_count -= 1
+        return self.reference_count
+
+    @property
+    def can_be_deleted(self) -> bool:
+        """是否可以物理删除（引用计数为0）"""
+        return self.reference_count == 0