init: 从 /root/zikai 根目录迁入

把原本散落在 /root/zikai 的 FastAPI 服务整理到 server/ 子目录，
开启独立 git 与 venv。运行时数据（config.yaml / keys / uploads）
按 .gitignore 留在工作目录但不入仓。

app/models/uploaded_file.py

@@ -0,0 +1,30 @@
+"""UploadedFile 实体。"""
+
+from __future__ import annotations
+
+from datetime import datetime
+
+from sqlalchemy import BigInteger, DateTime, String, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from ..database import Base
+
+
+class UploadedFile(Base):
+    __tablename__ = "uploaded_file"
+
+    id: Mapped[int] = mapped_column(BigInteger, primary_key=True, autoincrement=True)
+    # upload_dir 下的相对路径，例如 2026/06/<uuid>.bin
+    storage_path: Mapped[str] = mapped_column(String(512), nullable=False)
+    original_filename: Mapped[str] = mapped_column(String(512), nullable=False)
+    content_type: Mapped[str] = mapped_column(String(255), nullable=False, default="")
+    size_bytes: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
+    sha256: Mapped[str] = mapped_column(String(64), nullable=False, default="")
+    source: Mapped[str] = mapped_column(String(32), nullable=False, default="http")  # http / sftp
+    uploaded_by: Mapped[str] = mapped_column(String(128), nullable=False, default="")
+    uploaded_at: Mapped[datetime] = mapped_column(
+        DateTime, server_default=func.now(), nullable=False
+    )
+
+    def __repr__(self) -> str:  # pragma: no cover
+        return f"<UploadedFile id={self.id} name={self.original_filename!r} size={self.size_bytes}>"