fix: align network map builder with account isolation

backend/app/models/device_type.py

@@ -10,7 +10,7 @@ from app.core.database import Base
 
 
 class DeviceType(Base):
-    """A device type for network diagram nodes (system or team-custom)."""
+    """A device type for network diagram nodes (platform or account-custom)."""
     __tablename__ = "device_types"
 
     id: Mapped[uuid.UUID] = mapped_column(
@@ -32,11 +32,11 @@ class DeviceType(Base):
         Boolean, nullable=False, default=False,
         comment="True for built-in types that cannot be deleted",
     )
-    team_id: Mapped[uuid.UUID | None] = mapped_column(
+    account_id: Mapped[uuid.UUID] = mapped_column(
         UUID(as_uuid=True),
-        ForeignKey("teams.id", ondelete="CASCADE"),
-        nullable=True,
-        comment="NULL for system types, set for team-custom types",
+        ForeignKey("accounts.id", ondelete="CASCADE"),
+        nullable=False,
+        comment="Platform account for system types, tenant account for custom types",
     )
     sort_order: Mapped[int] = mapped_column(
         Integer, nullable=False, default=0,

backend/app/models/network_diagram.py

@@ -14,15 +14,15 @@ if TYPE_CHECKING:
 
 
 class NetworkDiagram(Base):
-    """A network topology diagram, team-scoped."""
+    """A network topology diagram scoped to one account."""
     __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(
+    account_id: Mapped[uuid.UUID] = mapped_column(
         UUID(as_uuid=True),
-        ForeignKey("teams.id", ondelete="CASCADE"),
+        ForeignKey("accounts.id", ondelete="CASCADE"),
         nullable=False,
         index=True,
     )