Remove customer-call_records relationship

app/models.py

@@ -75,9 +75,6 @@ class CallRecord(Base):
     created_at = Column(DateTime, default=datetime.utcnow)
     updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
 
-    # Relationship with customer
-    customer = relationship("Customer", back_populates="call_records")
-
     @classmethod
     def create_from_api(cls, customer_id: int, data: Dict) -> 'CallRecord':
         """Create a call record from API data"""