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

db/migrate/20250206204404_add_constraints_to_account_holdings.rb

@@ -0,0 +1,40 @@
+class AddConstraintsToAccountHoldings < ActiveRecord::Migration[7.2]
+  def up
+    # First, remove any holdings with nil values
+    execute <<-SQL
+      DELETE FROM account_holdings#{' '}
+      WHERE date IS NULL#{' '}
+         OR qty IS NULL#{' '}
+         OR price IS NULL#{' '}
+         OR amount IS NULL#{' '}
+         OR currency IS NULL;
+    SQL
+
+    # Remove any holdings where amount doesn't match qty * price
+    execute <<-SQL
+      DELETE FROM account_holdings#{' '}
+      WHERE ROUND(qty * price, 4) != ROUND(amount, 4);
+    SQL
+
+    # Remove any holdings with negative values
+    execute <<-SQL
+      DELETE FROM account_holdings#{' '}
+      WHERE qty < 0 OR price < 0 OR amount < 0;
+    SQL
+
+    # Now add NOT NULL constraints
+    change_column_null :account_holdings, :date, false
+    change_column_null :account_holdings, :qty, false
+    change_column_null :account_holdings, :price, false
+    change_column_null :account_holdings, :amount, false
+    change_column_null :account_holdings, :currency, false
+  end
+
+  def down
+    change_column_null :account_holdings, :date, true
+    change_column_null :account_holdings, :qty, true
+    change_column_null :account_holdings, :price, true
+    change_column_null :account_holdings, :amount, true
+    change_column_null :account_holdings, :currency, true
+  end
+end