Rescue Paperjet v1 implementation

backend/app/models/document.py

@@ -1,20 +1,25 @@
 """Document model — uploaded PDFs with soft-delete support."""
 
 import uuid
-from datetime import datetime, timezone
+from datetime import UTC, datetime
+from typing import TYPE_CHECKING
 
 from sqlalchemy import Index, Integer, Text
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from app.db import Base
 
+if TYPE_CHECKING:
+    from app.models.annotation_state import AnnotationState
+    from app.models.version import Version
+
 
 def _uuid() -> str:
     return str(uuid.uuid4())
 
 
 def _now_iso() -> str:
-    return datetime.now(timezone.utc).isoformat()
+    return datetime.now(UTC).isoformat()
 
 
 class Document(Base):