feat: add network_diagrams table

Create NetworkDiagram SQLAlchemy model with JSONB nodes/edges, team-scoped with client/asset metadata, and Alembic migration 074.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/models/__init__.py

@@ -55,6 +55,7 @@ from .fork_point import ForkPoint
 from .session_handoff import SessionHandoff
 from .session_resolution_output import SessionResolutionOutput
 from .device_type import DeviceType
+from .network_diagram import NetworkDiagram
 
 __all__ = [
     "User",
@@ -124,4 +125,5 @@ __all__ = [
     "SessionHandoff",
     "SessionResolutionOutput",
     "DeviceType",
+    "NetworkDiagram",
 ]

backend/app/models/network_diagram.py

@@ -0,0 +1,53 @@
+"""Network diagram model."""
+import uuid
+from datetime import datetime, timezone
+from typing import Optional, TYPE_CHECKING
+
+from sqlalchemy import String, Text, Boolean, DateTime, ForeignKey
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+from sqlalchemy.dialects.postgresql import UUID, JSONB
+
+from app.core.database import Base
+
+if TYPE_CHECKING:
+    from app.models.user import User
+
+
+class NetworkDiagram(Base):
+    """A network topology diagram, team-scoped."""
+    __tablename__ = "network_diagrams"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    team_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("teams.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    client_name: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
+    asset_name: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
+    description: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    nodes: Mapped[list] = mapped_column(JSONB, nullable=False, server_default="'[]'")
+    edges: Mapped[list] = mapped_column(JSONB, nullable=False, server_default="'[]'")
+    thumbnail_url: Mapped[Optional[str]] = mapped_column(Text, nullable=True)
+    is_archived: Mapped[bool] = mapped_column(
+        Boolean, nullable=False, default=False,
+    )
+    created_by: Mapped[Optional[uuid.UUID]] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("users.id"),
+        nullable=True,
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(timezone.utc)
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(timezone.utc),
+        onupdate=lambda: datetime.now(timezone.utc),
+    )
+
+    creator: Mapped[Optional["User"]] = relationship("User", foreign_keys=[created_by])