Initial commit with Phase 0 Scaffolding

backend/app/models/annotation_state.py

@@ -0,0 +1,32 @@
+"""AnnotationState model — current working annotation layer per document."""
+
+from datetime import datetime, timezone
+
+from sqlalchemy import ForeignKey, Text
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.db import Base
+
+
+def _now_iso() -> str:
+    return datetime.now(timezone.utc).isoformat()
+
+
+class AnnotationState(Base):
+    """
+    Current working annotation state for a document.
+
+    One row per document. `data` is a JSON text column containing
+    the full annotation array — opaque to the server except during export.
+    """
+
+    __tablename__ = "annotation_states"
+
+    document_id: Mapped[str] = mapped_column(
+        Text, ForeignKey("documents.id", ondelete="CASCADE"), primary_key=True
+    )
+    data: Mapped[str] = mapped_column(Text, default="[]")  # JSON array
+    updated_at: Mapped[str] = mapped_column(Text, default=_now_iso, onupdate=_now_iso)
+
+    # Relationships
+    document: Mapped["Document"] = relationship("Document", back_populates="annotation_state")