fix(api): remove TimestampMixin from models whose DB tables lack timestamp columns

Remove TimestampMixin (created_at/updated_at) from Purchase, PurchaseItem,
PriceHistory, Coupon, and ShrinkflationEvent models since their PostgreSQL
tables do not have those columns. This was causing 500 errors on
/api/v1/purchases and /api/v1/purchases/stats.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/cartsnitch_api/models/coupon.py

@@ -9,14 +9,14 @@ from sqlalchemy import Boolean, Date, DateTime, ForeignKey, Numeric, String
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from cartsnitch_api.constants import DiscountType
-from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.models.base import Base, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from cartsnitch_api.models.product import NormalizedProduct
     from cartsnitch_api.models.store import Store
 
 
-class Coupon(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+class Coupon(UUIDPrimaryKeyMixin, Base):
     """A coupon or deal for a product at a store."""
 
     __tablename__ = "coupons"

src/cartsnitch_api/models/price.py

@@ -9,7 +9,7 @@ from sqlalchemy import Date, ForeignKey, Index, Numeric, String
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from cartsnitch_api.constants import PriceSource
-from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.models.base import Base, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from cartsnitch_api.models.product import NormalizedProduct
@@ -17,7 +17,7 @@ if TYPE_CHECKING:
     from cartsnitch_api.models.store import Store
 
 
-class PriceHistory(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+class PriceHistory(UUIDPrimaryKeyMixin, Base):
     """A single price observation for a product at a store on a date."""
 
     __tablename__ = "price_history"

src/cartsnitch_api/models/purchase.py

@@ -18,7 +18,7 @@ from sqlalchemy import (
 )
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
-from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.models.base import Base, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from cartsnitch_api.models.price import PriceHistory
@@ -27,7 +27,7 @@ if TYPE_CHECKING:
     from cartsnitch_api.models.user import User
 
 
-class Purchase(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+class Purchase(UUIDPrimaryKeyMixin, Base):
     """A single shopping trip / receipt."""
 
     __tablename__ = "purchases"
@@ -61,7 +61,7 @@ class Purchase(UUIDPrimaryKeyMixin, TimestampMixin, Base):
     )
 
 
-class PurchaseItem(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+class PurchaseItem(UUIDPrimaryKeyMixin, Base):
     """Individual line item on a receipt."""
 
     __tablename__ = "purchase_items"

src/cartsnitch_api/models/shrinkflation.py

@@ -9,13 +9,13 @@ from sqlalchemy import Date, ForeignKey, Numeric, String
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from cartsnitch_api.constants import SizeUnit
-from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.models.base import Base, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from cartsnitch_api.models.product import NormalizedProduct
 
 
-class ShrinkflationEvent(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+class ShrinkflationEvent(UUIDPrimaryKeyMixin, Base):
     """Detected shrinkflation event — product size changed while price held or rose."""
 
     __tablename__ = "shrinkflation_events"