feat(dashboard): supporting schema, seed, catalog links, funnel/PM labels and API contract (merge resolution)

backend/app/models/catalog.py

@@ -130,13 +130,18 @@ class CategoryAttribute(Base):
 
 class Material(Base):
     __tablename__ = "materials"
-    # v2.6/v2.7: name is GLOBALLY unique; decoupled from categories.
+    # v2.6/v2.7: name is GLOBALLY unique; v2.8 re-links materials to the
+    # category taxonomy for the dashboard filter cascade (nullable — backfill
+    # from the legacy `topic` text runs in init_db.ensure_dashboard_schema).
     __table_args__ = (UniqueConstraint("name", name="uq_material_name"),)
     __mapper_args__ = {"eager_defaults": True}
 
     id: Mapped[uuid.UUID] = _uuid_pk()
     name: Mapped[str] = mapped_column(Text, nullable=False)
     topic: Mapped[str | None] = mapped_column(Text)  # تاپیک جلوی برنامه (Persian) — legacy
+    category_id: Mapped[uuid.UUID | None] = mapped_column(
+        ForeignKey("material_categories.id", ondelete="SET NULL")
+    )
     canonical_unit_id: Mapped[int] = mapped_column(
         ForeignKey("units.id", ondelete="RESTRICT"), nullable=False
     )
@@ -147,6 +152,7 @@ class Material(Base):
     )
 
     canonical_unit: Mapped["Unit"] = relationship(lazy="raise")
+    category: Mapped["MaterialCategory | None"] = relationship(lazy="raise")
     attribute_values: Mapped[list["MaterialAttributeValue"]] = relationship(
         back_populates="material", lazy="raise", passive_deletes=True
     )