feat: migrate ORM base to sqlmodel-ext, add file viewers and WOPI integration

- Migrate SQLModel base classes, mixins, and database management to
  external sqlmodel-ext package; remove sqlmodels/base/, sqlmodels/mixin/,
  and sqlmodels/database.py
- Add file viewer/editor system with WOPI protocol support for
  collaborative editing (OnlyOffice, Collabora)
- Add enterprise edition license verification module (ee/)
- Add Dockerfile multi-stage build with Cython compilation support
- Add new dependencies: sqlmodel-ext, cryptography, whatthepatch

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sqlmodels/wopi.py

@@ -0,0 +1,83 @@
+"""
+WOPI（Web Application Open Platform Interface）协议模型
+
+提供 WOPI CheckFileInfo 响应模型和 WOPI 访问令牌 Payload 定义。
+"""
+from uuid import UUID
+
+from sqlmodel_ext import SQLModelBase
+
+
+class WopiFileInfo(SQLModelBase):
+    """
+    WOPI CheckFileInfo 响应模型。
+
+    字段命名遵循 WOPI 规范（PascalCase），通过 alias 映射。
+    参考: https://learn.microsoft.com/en-us/microsoft-365/cloud-storage-partner-program/rest/files/checkfileinfo
+    """
+
+    base_file_name: str
+    """文件名（含扩展名）"""
+
+    size: int
+    """文件大小（字节）"""
+
+    owner_id: str
+    """文件所有者标识"""
+
+    user_id: str
+    """当前用户标识"""
+
+    user_friendly_name: str
+    """用户显示名"""
+
+    version: str
+    """文件版本标识（使用 updated_at）"""
+
+    sha256: str = ""
+    """文件 SHA256 哈希（如果可用）"""
+
+    user_can_write: bool = False
+    """用户是否可写"""
+
+    user_can_not_write_relative: bool = True
+    """是否禁止创建关联文件"""
+
+    read_only: bool = True
+    """文件是否只读"""
+
+    supports_locks: bool = False
+    """是否支持锁（v1 不实现）"""
+
+    supports_update: bool = True
+    """是否支持更新"""
+
+    def to_wopi_dict(self) -> dict[str, str | int | bool]:
+        """转换为 WOPI 规范的 PascalCase 字典"""
+        return {
+            "BaseFileName": self.base_file_name,
+            "Size": self.size,
+            "OwnerId": self.owner_id,
+            "UserId": self.user_id,
+            "UserFriendlyName": self.user_friendly_name,
+            "Version": self.version,
+            "SHA256": self.sha256,
+            "UserCanWrite": self.user_can_write,
+            "UserCanNotWriteRelative": self.user_can_not_write_relative,
+            "ReadOnly": self.read_only,
+            "SupportsLocks": self.supports_locks,
+            "SupportsUpdate": self.supports_update,
+        }
+
+
+class WopiAccessTokenPayload(SQLModelBase):
+    """WOPI 访问令牌内部 Payload"""
+
+    file_id: UUID
+    """文件UUID"""
+
+    user_id: UUID
+    """用户UUID"""
+
+    can_write: bool = False
+    """是否可写"""