feat: add sync columns and source_tree relationship to StepLibrary model

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/models/step_library.py

@@ -13,6 +13,7 @@ if TYPE_CHECKING:
     from app.models.account import Account
     from app.models.step_category import StepCategory
     from app.models.session import Session
+    from app.models.tree import Tree
 
 
 class StepLibrary(Base):
@@ -95,10 +96,26 @@ class StepLibrary(Base):
     # Soft delete
     is_active: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
 
+    # Sync tracking (flow-sourced steps)
+    source_tree_id: Mapped[Optional[uuid.UUID]] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey('trees.id', ondelete='SET NULL'),
+        nullable=True,
+        index=True
+    )
+    source_node_id: Mapped[Optional[str]] = mapped_column(String(255), nullable=True)
+    is_flow_synced: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    last_synced_at: Mapped[Optional[datetime]] = mapped_column(DateTime(timezone=True), nullable=True)
+
     # Relationships
     creator: Mapped["User"] = relationship("User", foreign_keys=[created_by])
     team: Mapped[Optional["Team"]] = relationship("Team")
     account: Mapped[Optional["Account"]] = relationship("Account", foreign_keys=[account_id], back_populates="step_library")
+    source_tree: Mapped[Optional["Tree"]] = relationship(
+        "Tree",
+        foreign_keys=[source_tree_id],
+        lazy="select"
+    )
     category: Mapped[Optional["StepCategory"]] = relationship("StepCategory")
     ratings: Mapped[list["StepRating"]] = relationship("StepRating", back_populates="step", cascade="all, delete-orphan")
     usage_logs: Mapped[list["StepUsageLog"]] = relationship("StepUsageLog", back_populates="step", cascade="all, delete-orphan")