Fix Account Holding validation and synchronization (#1818)

* Fix Account Holding validation and synchronization

Fixes #1781

- Add comprehensive validations for Account::Holding
- Implement validation to ensure amount matches qty * price
- Update Account::Syncer to include qty and price during synchronization
- Add database constraints for holding attributes and calculations

* Remove database check constraints for Account Holdings

Align with project convention of keeping complex validations in ActiveRecord
- Remove database-level check constraints for quantity, price, and amount
- Maintain database-level null and unique constraints
- Prepare for more flexible validation in the model layer

app/models/account/syncer.rb

@@ -99,6 +99,8 @@ class Account::Syncer
         account.holdings.build(
           security: holding.security,
           date: holding.date,
+          qty: holding.qty,
+          price: exchange_rate.rate * holding.price,
           amount: exchange_rate.rate * holding.amount,
           currency: to_currency
         )