Rescue Paperjet v1 implementation

backend/app/models/version.py

@@ -1,20 +1,24 @@
 """Version model — annotation state snapshots for history/recovery."""
 
 import uuid
-from datetime import datetime, timezone
+from datetime import UTC, datetime
+from typing import TYPE_CHECKING
 
 from sqlalchemy import ForeignKey, Index, Text
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.db import Base
 
+if TYPE_CHECKING:
+    from app.models.document import Document
+
 
 def _uuid() -> str:
     return str(uuid.uuid4())
 
 
 def _now_iso() -> str:
-    return datetime.now(timezone.utc).isoformat()
+    return datetime.now(UTC).isoformat()
 
 
 class Version(Base):
@@ -40,6 +44,4 @@ class Version(Base):
     # Relationships
     document: Mapped["Document"] = relationship("Document", back_populates="versions")
 
-    __table_args__ = (
-        Index("ix_versions_document_created", "document_id", "created_at"),
-    )
+    __table_args__ = (Index("ix_versions_document_created", "document_id", "created_at"),)