refactor(cleanup): delete legacy storefront routes, convert cart to re-exports

Phase 6 of storefront restructure plan - delete legacy files and convert
remaining cart files to re-exports.

Deleted legacy storefront route files (now served from modules):
- app/api/v1/storefront/auth.py (→ customers module)
- app/api/v1/storefront/profile.py (→ customers module)
- app/api/v1/storefront/addresses.py (→ customers module)
- app/api/v1/storefront/carts.py (→ cart module)
- app/api/v1/storefront/products.py (→ catalog module)
- app/api/v1/storefront/orders.py (→ orders/checkout modules)
- app/api/v1/storefront/messages.py (→ messaging module)

Converted legacy cart files to re-exports:
- models/schema/cart.py → app.modules.cart.schemas
- models/database/cart.py → app.modules.cart.models
- app/services/cart_service.py → app.modules.cart.services

This reduces API-007 violations from 81 to 69 (remaining violations
are in admin/vendor routes - separate migration effort).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/database/cart.py

@@ -1,78 +1,13 @@
 # models/database/cart.py
-"""Cart item database model.
+"""
+LEGACY LOCATION - This file re-exports from the canonical module location.
 
-Money values are stored as integer cents (e.g., €105.91 = 10591).
-See docs/architecture/money-handling.md for details.
+Canonical location: app/modules/cart/models/
+
+This file exists for backward compatibility. New code should import from:
+    from app.modules.cart.models import CartItem
 """
 
-from sqlalchemy import (
-    Column,
-    ForeignKey,
-    Index,
-    Integer,
-    String,
-    UniqueConstraint,
-)
-from sqlalchemy.orm import relationship
+from app.modules.cart.models.cart import CartItem
 
-from app.core.database import Base
-from app.utils.money import cents_to_euros, euros_to_cents
-from models.database.base import TimestampMixin
-
-
-class CartItem(Base, TimestampMixin):
-    """
-    Shopping cart items.
-
-    Stores cart items per session, vendor, and product.
-    Sessions are identified by a session_id string (from browser cookies).
-
-    Price is stored as integer cents for precision.
-    """
-
-    __tablename__ = "cart_items"
-
-    id = Column(Integer, primary_key=True, index=True)
-    vendor_id = Column(Integer, ForeignKey("vendors.id"), nullable=False)
-    product_id = Column(Integer, ForeignKey("products.id"), nullable=False)
-    session_id = Column(String(255), nullable=False, index=True)
-
-    # Cart details
-    quantity = Column(Integer, nullable=False, default=1)
-    price_at_add_cents = Column(Integer, nullable=False)  # Price in cents when added
-
-    # Relationships
-    vendor = relationship("Vendor")
-    product = relationship("Product")
-
-    # Constraints
-    __table_args__ = (
-        UniqueConstraint("vendor_id", "session_id", "product_id", name="uq_cart_item"),
-        Index("idx_cart_session", "vendor_id", "session_id"),
-        Index("idx_cart_created", "created_at"),  # For cleanup of old carts
-    )
-
-    def __repr__(self):
-        return f"<CartItem(id={self.id}, session='{self.session_id}', product_id={self.product_id}, qty={self.quantity})>"
-
-    # === PRICE PROPERTIES (Euro convenience accessors) ===
-
-    @property
-    def price_at_add(self) -> float:
-        """Get price at add in euros."""
-        return cents_to_euros(self.price_at_add_cents)
-
-    @price_at_add.setter
-    def price_at_add(self, value: float):
-        """Set price at add from euros."""
-        self.price_at_add_cents = euros_to_cents(value)
-
-    @property
-    def line_total_cents(self) -> int:
-        """Calculate line total in cents."""
-        return self.price_at_add_cents * self.quantity
-
-    @property
-    def line_total(self) -> float:
-        """Calculate line total in euros."""
-        return cents_to_euros(self.line_total_cents)
+__all__ = ["CartItem"]