Initial commit with Phase 0 Scaffolding

backend/app/models/version.py

@@ -0,0 +1,45 @@
+"""Version model — annotation state snapshots for history/recovery."""
+
+import uuid
+from datetime import datetime, timezone
+
+from sqlalchemy import ForeignKey, Index, Text
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.db import Base
+
+
+def _uuid() -> str:
+    return str(uuid.uuid4())
+
+
+def _now_iso() -> str:
+    return datetime.now(timezone.utc).isoformat()
+
+
+class Version(Base):
+    """
+    A snapshot of a document's annotation state at a point in time.
+
+    Versions serve as a safety net for accidental annotation loss.
+    `kind` is either 'manual' (user-created) or 'auto' (system-created
+    at safety boundaries like document close or before destructive ops).
+    """
+
+    __tablename__ = "versions"
+
+    id: Mapped[str] = mapped_column(Text, primary_key=True, default=_uuid)
+    document_id: Mapped[str] = mapped_column(
+        Text, ForeignKey("documents.id", ondelete="CASCADE"), nullable=False
+    )
+    label: Mapped[str | None] = mapped_column(Text, nullable=True, default=None)
+    data: Mapped[str] = mapped_column(Text, nullable=False)  # JSON snapshot
+    kind: Mapped[str] = mapped_column(Text, nullable=False)  # 'manual' | 'auto'
+    created_at: Mapped[str] = mapped_column(Text, default=_now_iso)
+
+    # Relationships
+    document: Mapped["Document"] = relationship("Document", back_populates="versions")
+
+    __table_args__ = (
+        Index("ix_versions_document_created", "document_id", "created_at"),
+    )